SYNOVIAL FLUID INVESTIGATIONS:

Masterthesis

Lithuanian University of Health Sciences Faculty of Medicine

Department of Rheumatology Kaunas, 2019

SYNOVIAL FLUID INVESTIGATIONS:

VALUE FOR THE DIAGNOSIS OF MONOARTHRITIS

Author:

Susanne Sophie Wenk

Medical Student, 6

Course

Supervisor:

Egidijus Eviltis

Doctor of Rheumatology

Department of Rheumatology

Kauno Klinikos

TABLE OF CONTENTS

1. SUMMARY 3

2. CONFLICT OF INTERESTS 4

3. ETHICS COMMITTEE APPROVAL 5

4. ABBREVIATIONS LIST 6

5. TERMS 7

6. INTRODUCTION 8

7. AIM & OBJECTIVES 9

8.1 Aim 9

8.2 Objectives 9

9. LITERATURE REVIEW 10

9.1 Significance of Musculoskeletal Diseases 10

9.2 Arthrocentesis as a Diagnostic Tool 10

9.3 Synovial Fluid Investigations 11

9.4 Diagnosis of Mono-articular Osteoarthritis 11

9.5 Diagnosis of Mono-articular Gout 12

9.6 Diagnosis of Mono-articular Septic Arthritis 12

9.7 Diagnosis of Mono-articular Pseudo-gout 13

10. RESEARCH METHODOLOGY & METHODS 14

11. RESULTS AND THEIR DISCUSSION 16

11.1 Mono-arthritic Diseases 16

11.2 Age & Sex 17

11.3 Number of Synovial Fluid Investigations 18

11.4 Synovial Fluid Culture Results 19

11.5 Synovial Fluid Investigation Results 20

11.51 Colour 20

11.52 Transparency 20

11.53 Viscosity 21

11.54 Crystals 22

11.55 Red Blood Cells 22

11.56 White Blood Cells 23

11.57 Polymorphonuclear Neutrophils 24

11.6 Other Diagnostic Tests Performed 24

12. CONCLUSIONS 26

13. LITERATURE LIST 27

1. SUMMARY

This master-thesis with the title “Synovial Fluid Investigations: Value for the Diagnosis of Mono- arthritis” was written by Susanne Sophie Wenk. The aim is to determine the value of synovial fluid (SF) in diagnosing mono-arthritic diseases. For this purpose the methodology of patient file analysis was chosen. 166 files of patients that were treated for a mono-arthritic disease in Kauno Klinikos, rheumatology department, in between the years 2012 to 2015 were selected and retrospectively analysed. It was reviewed how often synovial fluid investigations (SFI), including synovial fluid cultures (SFC), were performed and the results of the SFI were compared to the expected outcome for each disease category.

Musculoskeletal diseases are becoming more and more prevalent all over the world within all society classes, mono-arthritic diseases are a part of that. In order to battle the growing strain of arthritis on our community more research into the matter is required to establish how the quality of life for the patients can be improved and the costs reduced. One very important factor is an early and reliable diagnosis, not only to treat the disease but also to prevent permanent sequelae and even death.

Mono-arthritis (MA) is linked to many co-morbidities that are becoming an increasing problem in developed countries, such as diabetes mellitus, obesity, kidney failure, our changed life-style including diet habits and drug intake, such as diuretics. MA can be caused by multiple diseases, the most

common one being gout, followed by septic arthritis (SA) and not classified MA (NC-MA). For most mono-arthritic diseases the diagnostic tool with the highest specificity and sensitivity is the SFI via arthrocentesis. In this sterile procedure some SF is obtained via needle puncture of the joint and is then analysed in a laboratory. SFC, gross appearance of the SF, cell count or crystal content detection is very helpful in differentiating arthritic diseases and making a diagnosis, however SFI are not yet a routine examination for MA patients.

The results of this thesis show that the SFI is a reliable tool in detecting inflammatory SF. The gross appearance, viscosity, white blood cell (WBC), red blood cell (RBC) and polymorphonuclear neutrophil (PMN) count significantly change during SA and gout. However, the SFC was not established as a sensitive test in this investigation since only 35% of cultures were positive in SA patients. In crystal-associated diseases specific crystals weren't found in 70% of patients diagnosed with gout.

All in all the SFI is a reliable diagnostic tool in detecting inflammatory SF, but in this investigation the

SFI was not valuable in diagnosing MA diseases.

3. CONFLICT OF INTERESTS

The author reports no conflict of interests.

4. ETHICS COMITTEE APPROVAL

The LSMU Bioethics Centre supports, after evaluating the documents submitted by Susanne Sophie

Wenk, the students research work with the title “Synovial Fluid Investigation: Value for Diagnosis of

Mono-Arthritis”. Case number BEC-MF-158. Issued on the 10

of December 2018.

5. ABBREVIATIONS LIST

BC Blood Culture

CBC Complete Blood Count

CPP Calcium Pyrophosphate

CRP C-Reactive Protein

Dr Doctor

F Female

Fig. Figure

JMRI Joint Magnetic Resonance Investigation

JUS Joint Ultrasound

JXR Joint X-Ray

M Male

MA Mono-arthritis

MSU Mono-Sodium Urate

NC-MA Not Classified Mono-arthritis

No. Number

OA Osteoarthritis

PCR Polymerase-Chain-Reaction

PMN Polymorphonuclear Neutrophils

Prof Professor

P-G Pseudo-gout

RBC Red Blood Cell

SA Septic Arthritis

SF Synovial Fluid

SFI Synovial Fluid Investigation

SFC Synovial Fluid Culture

UA Urine Analysis

UC Urine Culture

US Ultrasonography

WBC White Blood Cell

WHO World Health Organization

6. Terms

Arthrocentesis A procedure in which synovial fluid is obtained from the joint via needle puncture.

Podagra Inflammation of the first metatarsophalangeal joint usually due to gout.

Synovial Fluid A clear fluid inside the joint serving mainly as lubrication.

7. INTRODUCTION

In this thesis the value of SFI for the diagnosis of MA is analysed. In detail specific mono-arthritic diseases, such as gout, pseudo-gout (P-G), SA, osteoarthritis (OA) and NC-MA, are being discussed.

Musculoskeletal diseases are not given the health priority needed, even though these diseases are found in all parts of the world and in all society classes and they are the „commonest cause of long- term pain and physical disability“ worldwide and affect the patients quality of life severely. In the European countries almost 25% of adults claim to have “some sort of arthritis or rheumatism”.

Doctors estimate that the incidence of diagnosed arthritis will increase yearly, therefore the costs will also increase, for example in the USA from 54.4 million in 2013-2015 to 78.4 million (25.9%) in 2040.

Arthritis is linked to co-morbidities of our modern society in which the number of cases are rising dramatically every year as well, such as obesity, diabetes mellitus and heart diseases.

Symptoms of MA may involve redness, pain, swelling, warmth and dysfunction of the affected joint.

During the process of joint aspiration, also called arthrocentesis, a sterile needle is inserted into the joint space and SF is drained. It can be used as a diagnostic tool, e.g. for growing a SFC, analysing cells and other contents of the fluid, or as therapeutic instrument. Because most rheumatological diseases often involve more than one joint there should always be the suspicion of an “urgent

condition”, such as “SA [and] acute crystal induced arthritis” in which a fast diagnosis is essential in avoiding “significant morbid or mortal sequelae”.

A SFC and SFI are specific and effective ways of confirming or excluding SA. Gout and P-G can also be diagnosed using a SFI by analysing the crystal content. On the other hand in OA and NC-MA a joint aspiration may only be useful for excluding other diseases, other investigation methods are used much more commonly, such as a joint x-ray (JXR) or joint ultrasound (JUS).

In Lithuania, Kauno Klinikos in particular, no scientific analysis or scientific article about SF in MA was found. A fast and correct diagnosis is important in management and treatment of joint diseases and is therefore of highest importance during the hospitalization of the patient. For this purpose the

methodology of patient file analysis was chosen. Previously hospitalized patients with a diagnosis of a mono-arthritic disease in the Kauno Klinikos hospital in Kaunas, Lithuania, department of

rheumatology, between the years 2012 and 2015, were selected, analysed and compared.

The aim of this thesis is to estimate the value of a SFI in diagnosing a mono-arthritic disease.

8. AIM & OBJECTIVES

8.1 AIM

The aim of this thesis is to estimate the value of a synovial fluid investigation in diagnosing a mono- arthritic disease.

8.2 OBJECTIVES:

1. What diseases cause MA most commonly?

2. How often are SFIs performed in mono-arthritic patients?

3. How sensitive are SFCs in patients with SA?

4. What are the changes in gross appearance (colour, transparency) and viscosity in inflammatory MA?

5. How sensitive is the detection of crystals in crystal-associated diseases (gout, P-G)?

6. How do the No. of RBC, WBC and PMN change in inflammatory MA?

7. What other tests helped in the diagnosis of MA?

9

9. LITERATURE REVIEW

9.1 SIGNIFICANCE OF MUSCULOSKELETAL DISEASES

According to the WHO the prolonged life expectancy together with our changed life-style and diet habits has lead to a new serious health issue in both developing and industrialized countries: non- communicable diseases. Chronic conditions, to which OA, gout and P-G can be classified to, are becoming more and more prevalent. Musculoskeletal or rheumatic diseases are the main cause of morbidity today and have a severe impact on the patients health and quality of life. The strain on the health care and community support will increase due to the growing number of patients with a disabling disorder. Therefore it is important to establish guidelines for collecting data, a uniform staging and definition of the diseases in order to have reliable data for dealing with the issue of chronic diseases.

One disorder belonging to this group of musculoskeletal diseases is MA, which is by definition the inflammation of a single joint. Because MA can initially present in most joint diseases, it's important to suspect in every patient with mono-articular disease a pyogenic infection until proven otherwise, because SA is a medical emergency. To diagnose arthritic diseases as early as possible in order to prevent sequelae and permanent complications is essential. However, most patients diagnosed with MA have a subacute or chronic disease progression.

9.2 ARTHROCENTESIS AS A DIAGNOSTIC TOOL

Arthrocentesis is a valuable diagnostic procedure in differentiating joint diseases, such as infection, crystal arthropathy, OA and other. The main indications as diagnostic tool are as followed: evaluation of MA, identify cause of unexplained joint effusion, rule out joint infection/limit joint damage from an infectious process, [...] and identify crystal-induced arthropathy. The importance of arthrocentesis lays in a fast and reliable diagnosis, since disability and mortality increase with delayed diagnosis of especially bacterial arthritis. Peripheral blood tests lack specificity in establishing a diagnosis of these diseases.

SFI has been widely recommended as a valuable tool in diagnosing arthritis, many rheumatologists even consider it to be the most important laboratory test. SF can reflect the degree of joint

inflammation and SFI is a simple way in distinguishing different diseases.

Pathological SF can be classified into non-inflammatory (e.g. osteoarthritis), inflammatory (e.g. acute

gout, acute P-G), purulent (e.g. SA) and haemorrhagic types. Following procedures advised to be

performed as routine for arthritis diagnosis: microbiological examination (including SFC and gram

stains), WBC count, microscopic wet smear examination (for crystals) and lastly various chemical (e.g.

glucose) and immunological analysis. If SF would be examined systematically and the result used in conjunction with other investigative tools a ”maximum of information [could] be obtained”.

9.3 SYNOVIAL FLUID INVESTIGATIONS

During the laboratory investigation of SF following steps are performed: physical examination (eg appearance, colour, viscosity), chemical analysis (eg glucose, total protein level, uric acid) and microscopic evaluation (eg cell count, crystal identification). Normal characteristics of SF include a clear appearance, WBC less than 200 cells/μL, PMNs less than 25%, a high viscosity, a glucose level similar to the patients blood glucose level.

Indications for SFI include all patients presenting with a joint effusion or inflammation, without a known cause. SF cultures and gram stain are especially useful in diagnosing SA.

SFI is a safe procedure and helps in differentiating different arthritic diseases. In SA and crystal arthritis SF is the basis for a definite diagnosis, but SF also provides useful information in recognizing the degree of joint inflammation and presence of haemarthrosis. Non-specific SF changes include increased SF volume, cell count and turbidity, reduced viscosity and an increasing ratio of PMN cells.

Specific changes include the presence of crystals (eg MSU, CPP).

9.4 DIAGNOSIS OF MONO-ARTICULAR OSTEOARTHRITIS

In OA, a non-inflammatory joint disease, the “cornerstone of diagnosis” is the plane film x-ray examination because it shows specific macroscopic changes in the joint. A SFI is usually without pathological changes and is only recommended if the diagnosis can't be made without excluding other conditions, such as crystal-associated arthritis or SA. The diagnosis of other arthritic diseases with a SFI is important in order to prevent secondary OA.

Only if the patient has symptoms of OA and pathological radiological changes, which include

“narrowing of joint space width, osteophyte formation, […] subchondral sclerosis and cysts”, the diagnosis is made, however only in advanced stages those symptoms and changes develop. In this stage the disease is most probably irreversible. For early diagnosis these diagnostic criteria have only limited value. MRI is “more sensitive in detecting early structural changes” and is recommended for cartilage assessment by the Osteoarthritis Research Society International for an early detection of OA.

US is valuable in assessing the synovium and to find changes suggesting synovitis. CT is not

commonly used for the diagnosis. Biochemical markers, such as “precursors or degradation products

of collagen and proteoglycan”, can be found in blood, urine or SF, the sensitivity and specificity

however is poor.

In order to detect OA as early as possible the diagnosis of synovitis via biopsy may be established, since synovitis is common in both early and late forms of this disease.

9.5 DIAGNOSIS OF MONO-ARTICULAR GOUT

Gout is an inflammatory condition often found in the lower extremities, especially the

metatarsophalangeal joint. It's the most common arthritic form in men and is causing, in it's acute form, mainly MA. US can detect gout already in it's early stages, but to have a definite diagnosis mono-sodium urate (MSU) crystals must be detected in the SF via SFI. A professional examiner can find those crystals with a sensitivity of 95.3% and a specificity of 97.2%. If no crystals are detected gout can't be excluded for sure. With the SFI gout can be differentiated from P-G, which may have the same symptoms. For differential diagnosis other imaging techniques may be used, such as x-ray.

However, typical pathological x-ray changes can only be seen in chronic gout with tophi.

Hyperuricemia (serum uric acid >380 μmol/L or >6.4 mg/dL), leucocytosis, elevated CRP or ESR, tophi and radiological changes are all indications for gout that should also be evaluated and are important in conjunction with the needle-shaped MSU crystals in the SF. The metabolic syndrome and hypertension are clearly associated with this disease.

Performing a SFI to find evidence of MSU crystals is a golden standard procedure in establishing a definite diagnosis. Usually following a clinical appearance strongly suggesting gout an arthrocentesis is performed to look for the needle-shaped, 2 to 20 mm long crystals. Certain studies however have shown that not always those crystals can be identified in gout patients, this is assumed to be linked to poorly performing laboratories.

9.6 DIAGNOSIS OF MONO-ARTICULAR SEPTIC ARTHRITIS

SA is a purulent form of MA due to an infection with bacteria, the main one being Staphylococcus

Aureus causing over 50% of MA cases. Even though the disease is rare, only 4-10 cases per 100,000

inhabitants, it is not to be underestimated as SA is a rheumatological emergency. Recognizing the

condition and the interdisciplinary diagnosis can be a challenge. Only in 10% of cases the patient

comes with oligoarthritis, 90% is MA. Because of the importance in treating SA as fast and consequent

as possible, the diagnosis is to be assumed until it can be excluded with certainty. The laboratory

diagnostic shows an increase in CRP and later ESR and a leucocytosis (neutrophilic). For early

diagnosis the SFI with SFC has a special importance and is to be done before starting the treatment

with antibiotics, however in 20% of cases there is no growth in the SFC. X-ray is part of the basic

diagnostic tools, as well as US, but MRI and scintigram are not needed in emergency situations and

more useful in chronic SA.

Viscosity (low) and appearance (turbid, sanious) of the SF during the analysis can be the first

indicators for an infection. A high number of leucocytes (>50,000/μl) and a granulocyte share of over 90% are very typical signs, however can also be found in many other MA causing conditions. Low numbers of leucocytes can't exclude the diagnosis of SA. Gram staining has compared to SFC a lower sensitivity (up to 50%) but the advantage of a fast result. If the SFC shows no growth other diagnostic techniques, such as PCR, may be required. For differential diagnosis crystal-associated conditions should be excluded. Other relevant laboratory tools are blood cultures (as a routine procedure) and urine cultures or a genital swabs if an extra-articular focus is suspected.

Around 24% of blood cultures were found positive in septic arthritis of the knee, 9% being the only positive microbiological diagnosis. “The key to the diagnosis of suspected […] infection is immediate microscopic analysis and culture of SF” and SFC is “considered the gold standard for diagnosis”.

Nevertheless high rates of false-negative and false-positive results are documented. PCR is more sensitive. X-ray images have no benefit in diagnosing, but may be performed as “baseline investigation”.

9.7 DIAGNOSIS OF MONO-ARTICULAR PSEUDO-GOUT

P-G is a disease characterized by calcium pyrophosphate (CPP) crystal depositions in the synovium and periarticular soft tissues. The disease is suspected when the patients presents with the typical clinical picture and radiographic or laboratory findings, however definite diagnosis is based on the detection of CPP crystals in SF using microscopy methods, such as light microscopy, compensated polarized light microscopy or phase contrast microscopy.

The SFI sensitivity and specificity is very high, therefore SFI is the gold standard in diagnosing P-G.

Even one or a few crystals in the SF are clinically significant. The diagnosis gains more confidence the more characteristic the crystal morphology is.

When SFI is not available, CPP crystals may be detected using imaging techniques, the most accurate being US. While the sensitivity in radiography is low, US appears to be highly specific and sensitive in demonstrating the presence of CPP crystals. Additionally calcifications of hyaline cartilage and

fibrocartilage may be seen.

13

10. RESEARCH METHODOLOGY & METHODS

This study was conducted in the rheumatology department of the Kauno Klinikos hospital in Kaunas, Lithuania. In order to investigate the value of SF in diagnosing MA the methodology of patient file analysis was chosen. 166 files of patients treated for a mono-arthritic disease in between the years2012 to 2015 were selected. All patients live in Lithuania, except one that lives in Germany. The patients presented with different diseases, such as gout, P-G, OA, SA and NC-MA. In order to analyse the files statistics were established:

1. MA patients were put into disease categories according to their diagnosis.

2. Age and sex of the patients were registered.

3. The number of SFI and SFC performed was noted.

4. The outcome of SFC was noted.

5. Pathological changes in the SF were compared to the expected outcome according to each disease category.

6. Other diagnostic tests which were used in the diagnosing process were viewed.

For evaluating the SFI results the norm values from the Kauno Klinikos Laboratory were used, as seen in Table 1: Norm Values for SFI.

Table 1: Norm Values for Synovial Fluid Investigations Colour Transparency Viscosity (cm) Crystals RBC

(x10^9/L)

WBC (x10^6/L)

MN% PMN%

Transparent Clear >3 No 0 <200 >75 <25

*source: Kauno Klinikos Laboratory

In order to analyse typical changes of the investigated MA diseases Table 2: Expected Outcome for

Specific MA Diseases was used to compare pathological changes in the SFI to the expected changes

related to the disease. The diseases in which no SFI was performed (NC-MA and OA) were not

considered in this table.

Table 2: Expected Outcome for Specific Mono-arthritic Diseases Colour Transp

arency

Viscosity Crystals RBC WBC PMN%

Gout Yellow or yellowish

Cloudy Decreased MSU crystals

Negative to slightly increased

Slightly to extremely increased

Dominant

P-G Yellow or

yellowish Cloudy Decreased CPP

crystals Negative to slightly increased

Slightly to extremely increased

Dominant

SA Purulent yellow

Opaque or cloudy

Decreased Negative Negative to slightly increased

Extremely increased

Dominant (moderately to extremely

increased)

*sources: SA

, gout

, P-G

, SF findings by disease category

To be able to evaluate the results of the SFI different grades of pathological change was elaborated as seen in Table 3: Grades of Pathological SFI Changes.

Table: SFI Reference

Table 3: Grades of Pathological Synovial Fluid Changes

Viscosity (cm) WBC *10^6/l PMN% RBC *10^9/l

Slightly Increased <3000 25-50 1-20

Moderately Increased 3000-50,000 51-90 21-100

Severely Increased >50,000 >90 >100

Slightly Decreased 2.1-3

Moderately Decreased 1-2

Severely Decreased <1

11. RESULTS AND THEIR DISCUSSION

11.1 MONO-ARTHRITIC DISEASES

By selecting patients with a mono-arthritic disease treated at the rheumatology department of Kauno Klinikos, Lithuania, between the years 2012 until 2015, 166 patient files were collected.

These files were sorted according to their main diagnosis. The results can be seen in Figure (Fig.) 1:

Patient Files According to their Diagnosis.

Fig.1: Patient Files According to their Diagnosis (N166)

As presented in Fig.1 the majority of patients were diagnosed with gout (72/166).

During the first acute attacks gout is often mono-articular and involves the big toe (podagra).

Gout is “the most prevalent form of inflammatory arthropathy [and] prevalence and incidence have risen in recent decades”. The reason may be the increase of risk factors in our modern society, such as hyperuricaemia, dietary factors, alcohol consumption, the metabolic syndrome, hypertension, diuretic use, obesity and chronic renal disease.

The global burden of gout has been increasing substantially over the last decades, developed countries seem to have a higher prevalence and incidence rate which can be explained by socio-economic, genetic and dietary factors, as well as co-morbidities and medications influencing the uric acid level and MSU crystal formation.

SA was diagnosed in 53/166 patients making it the second most prevalent cause of MA.

In 80% of cases septic arthritis only affects a single joint, usually the knee joint, and the prevalence is higher in patients in extreme ages and with co-morbidities. In developed countries cases of SA seem to

43.40%

4.80%

31.90%

4.20%

15.70%

Gout

Pseudo-Gout

Septic Arthritis

Osteoarthritis

Not Classified MA

be increasing (2-6 cases/100,000 inhabitants annually).

The rising of SA cases may be linked to augmented orthopaedic-related infection, high age, immunosuppressive therapy and an increase of invasive procedures.

26/166 patients presented with NC-MA. NC-MA is usually diagnosed by excluding other diseases or if the aetiology of MA is unknown.

Only 8/166 suffered from P-G and 7/166 from OA.

OA “symptoms usually present in just one or a few joints”.

But since the No. of OA cases were so low, the results of the OA patients are not representative in this investigation. The low number of patients with OA may be explained by a late diagnosis of OA, so that multiple joints are already affected.

Since the patient number in P-G were very low the results for this disease category is not representative in this investigation.

A literature review about acute MA from 2009 shows that 16%-36% of patients presented with MA of an unkown cause (NC-MA), 15%-27% were diagnosed with gout and 8%-27% with SA, followed by 5%-17% with OA.

11.2 AGE & SEX

In Table 4: Age and Sex the distribution of patients mean age and sex among the diseases with mono- arthritic form can be seen.

Table 4: Age and Sex

Age in years (mean) Sex (total No.)

Gout F: 72.1; M: 59.6 F: 8; M: 64

P-G F: 70.3; M: 64.4 F: 3; M: 5

SA F: 56.2; M: 45.4 F: 29; M: 24

OA F: 48.7; M: 63 F: 6; M: 1

NC-MA F: 55.8; M: 53.1 F: 17; M: 9

Total F: 58.1; M: 56 F: 63; M: 103

Most patients (ca. 62%) are of male sex, while around 38% are females. The average age in males is 56 years, in females 58.1 years. However, in each disease category the mean age and dominant sex differs. In the disease category gout women are a lot older (72.1 years) than men (59.6 years), while gout is by far more common in men (64 out of 72).

“Gout tends to occur earlier in life in men than women”

and “is the most common form of

The patients with SA are insignificantly more commonly women. Also the patients are younger than in other disease categories, especially the men (45.4 years).

An 18 year clinical review states that “males [are] affected more than females”

and “45% are older than 65 years”.

However, this review results can't be compared to the results of this investigation because of the different methodology and approach.

P-G patients were more often male and around 70 years old. OA is more common in females who are around 49 years old. In the category NC-MA there are almost double as much females, however the age in both gender is very similar, between 53 and 55 years.

In this investigation MA patients were predominately male (103/166) and the mean age for both genders was in the late 50s (females 58.1 years, males 56 years).

According to a follow up study from 2007 females patients predominate in MA while the mean age is around 48 years.

11.3 NUMBER OF SYNOVIAL FLUID INVESTIGATIONS

The amount of SFI and SFC performed in each disease category can be seen in the following table Fig.

2: No. of SFI and SFC Performed.

Fig. 2: No. of Synovial Fluid Investigations and Synovial Fluid Cultures Performed

A SFI was performed in every 5

patient that was diagnosed with MA (34/166), a SFC in every 3

patient (55/166).

In 4/26 patients diagnosed with NC-MA a SFC was performed, but no SFI at all. Patients presenting with OA received neither a SFI nor a SFC. Most SF procedures were done with SA patients. 19/53

Gout Pseudogout Septic Arthritis Osteoarthritis Not Classified MA Total

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 13.90%

62.50%

35.90%

0.00%

0.00%

20.50%

11.10%

37.50%

75.50%

0.00%

15.40%

33.10%

Patients with SFI

Patients with SFC

In 5/8 patients with P-G a SFI and in 3/8 patients a SFC got carried out. Only a minority of patients with gout received a SFI (10/72) or a SFC (8/72).

Results from a prospective cohort study revealed that “the most accurate tests” for patients arriving with MA in the emergency department included besides JXR SFI.

Since SFIs including SFCs are standard tests in diagnosing MA diseases the rate of patients receiving an arthrocentesis and SF testing is lower than expected.

11.4 SYNOVIAL CULTURE RESULTS

Since no SFC were performed in patients diagnosed with OA this disease category was not taken into account. As seen in Fig. 3: SFC Results in gout, P-G and NC-MA the SFC results were negative, as expected, only in patients presenting with SA 14 out of 40 were positive. 35% of positive SFC in SA seems quite low.

According to a systematic review from 2007 about septic arthritis management “culture of synovial fluid [is a] fundamental diagnostic tool […] the sensitivity of detection of causative organisms is, however, often disappointing.”

During the procedure of culturing and microscopic identification of a possible pathogen a WBC increase was noted in the majority of cases, in 4/8 patients with gout, in 2/3 patients with P-G, in 30/40 patients with SA and in 2/4 patients with NC-MA.

Fig. 3: Synovial Fluid Culture Results

Gout

Pseudogout

Septic Arthritis

Not Classified MA 0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.00% 0.00%

35.00%

0.00%

100.00% 100.00%

65.00%

100.00%

50.00%

66.67%

75.00%

50.00% Positive Negative

Increase in WBC

11.5 SYNOVIAL FLUID INVESTIGATION RESULTS

11.51 Colour

As seen in Fig. 4: SFI Colour Results the SF colour found most commonly is yellow. Only in SA some patients have a high amount of RBC in their SF, therefore the colour is red. Also in gout and P-G some RBCs can be suspected, since the second most common SF colour is pink.

Fig. 4: Synovial Fluid Investigation Colour Results

The SF colour results confirm the expected outcome of a majority of SFI with yellow colour (see Table 3: Expected Outcome for Specific MA Diseases). Normal SF should be transparent. The colour yellow suggests a inflammatory (gout or P-G) or even purulent (SA) disease, due to the increasing amount of plasma and nucleated cells. The colour pink indicated the presents of some RBC while the colour red indicates many RBC (haemorrhagic). The shade yellowish shows an inflammatory tendency.

11.52 Transparency

The physical examination of SF in terms of transparency can be seen in Fig. 5: SFI Transparency Results. The majority of SF in MA is cloudy, in SA even over 94%. In gout and P-G not a single test revealed a clear SF. The increased opacity causing the SF to become cloudy is due to an increased amount of nucleated or RBCs, but can also be caused by acellular material, such as lipids or crystals.

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

20.00%

0.00%

26.32%

40.00%

60.00%

36.84%

30.00%

40.00%

10.52%

0.00%

0.00%

26.32%

10.00%

0.00%

0.00%

Transparent

Yellowish

Yellow

Pink

Red

Not Tested

Fig. 5: Synovial Fluid Inestigation Transparency Results

All in all the gross examination of clarity seems to be a reliable test in differentiating non- inflammatory to inflammatory SF.

11.53 Viscosity

Fig. 6: SFI Viscosity Results shows that generally the viscosity seems to decrease in MA. Only in P-G 40% of tests revealed a normal viscosity, in SA and gout slightly to severely decreased viscosity prevails. Proteolytic enzymes in inflamed SF or purulent effusions are the cause of decreased viscosity.

Fig. 6: Synovial Fluid Investigation Viscosity Results

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.00%

0.00%

5.26%

90.00%

80.00%

94.74%

10.00%

20.00%

0.00%

Clear Cloudy Not Tested

Gout P-G SA

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 10.00%

40.00%

15.78%

20.00%

0.00%

31.58%

30.00%

20.00%

10.53%

20.00%

20.00%

31.58%

20.00%

20.00%

10.53%

Norm

Slightly Decreased

Moderately Decreased

Severely Decreased

Not Tested

11.54 Crystals

As seen in Fig. 7: SFI Crystal Results the majority of SFIs could not prove the existence of crystals. In gout 50% of SFI revealed crystals, only 30% being the disease specific MSU crystals.

Since most scientific articles agree that the detection of disease specific crystals is a gold standard for diagnosing both gout and P-G, the SFI results obtained are very surprising. From all patients diagnosed with gout only 13.9% of patients SF (see Fig. 2: No. of SFIs and SFCs Performed) was analysed and from those only 30% of patients were identified with MSU crystals in their SF. Because P-G has the same clinical picture as gout “the difference is seen when evaluating crystals through a polarizing microscope” only

and it's the only test ensuring a “definite diagnosis” with a sensitivity of 95.3%

and a specificity of 97.2%.

But that seems to depend on the laboratory evaluating the SF.

0% of P-G patients were identified with the disease specific CPP crystals, 80% having no crystals at all.

Fig. 7: Synovial Fluid Investigation Crystal Results

11.55 RBCs

Most MA patients present with a slightly increased No. of RBCs in their SF, as can be seen in Fig. 8:

SFI RBC Results. Around 20% of patients are within the norm values. In gout and SA some patients have a moderately or severely increased No. of RBC, not so in patients with P-G in which 80% of patients SF showed a slight increase of RBCs.

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 30.00%

0.00%

5.26%

10.00%

0.00%

5.26%

10.00%

20.00%

0.00%

50.00%

80.00%

78.95%

0.00%

0.00%

10.53%

MSU crystals CPP crystals Unspecified crystals Negative

Not Tested

Fig. 8: Synovial Fluid Investigation RBC Results

11.56 WBCs

Fig. 9: SFI WBC Results shows that a dominant factor in MA is a moderately increased No. of WBC in the SF. While in SA patients presented with moderately to severely increased WBCs, patients with gout or P-G presented with slightly to moderately increased WBCs. The WBC SFI results match the expected outcome for these diseases (see Table 2: Expected Outcome for Specific MA Diseases).

Fig. 9: Synovial Fluid Investigation WBC Results

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 20.00%

20.00%

21.05%

40.00%

80.00%

42.11%

10.00%

0.00%

15.79%

10.00%

0.00%

15.79%

20.00%

0.00%

5.26%

Norm

Slightly Increased Moderately Increased Severely Increased Not Tested

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.00%

0.00%

10.53%

20.00%

20.00%

0.00%

50.00%

80.00%

57.89%

10.00%

0.00%

31.58%

20.00%

0.00%

0.00%

Norm

Slightly Increased

Moderately Increased

Severely Increased

Not Tested

11.57 Polymorphic Mononuclear Neutrophils

A moderate increase of PMNs was noted in most patients with MA. Fig. 10: SFI PMN (%) Results shows that PMNs severely increased in the majority of cases, closely followed by a moderate increase.

In gout and P-G PMNs increased moderately, 20% severely. The results match the expected outcome for these diseases (see Table 2: Expected Outcome for Specific MA Diseases).

Fig. 10: Synovial Fluid Investigation Polymorphic Mononuclear Neutrophils (%) Results

11.6 OTHER DIAGNOSTIC TESTS PERFORMED

What other diagnostic tests were performed in order to diagnose MA can be seen in Table 5: Other Diagnostic Tests Performed. Between 87.5% (P-G) to 100% (OA) of patients blood was evaluated. On the majority a JXR was performed, especially if patients were suspected to have OA or P-G, except in patients later diagnosed with NC-MA only in 46.2% of cases a JXR was ordered. While in NC-MA patients only 30.8% were tested via JUS, up to 87.5% of P-G and 84.9% of SA patients joints got analysed using ultrasound (US). JCT and JMRI was only used on very few patients. Blood cultures (BC) were mainly performed on patients with SA (71.7%), in other MA diseases only from 23.6%

(gout) to 30.8% (NC-MA). Urine analysis (UA) was performed as a routine for the majority of patients, urine culture (UC) however mainly for patients suspected of having an infectious disease:

45.3% of SA patients received a UC, but only 12.5% (P-G) to 23.1 (NC-MA) patients of other MA diseases.

Gout P-G SA

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

10.00%

0.00%

5.26%

10.00%

0.00%

0.00%

40.00%

60.00%

42.11%

20.00%

20.00%

47.37%

20.00%

20.00%

5.26%

Norm

Slightly Increased

Moderately Increased

Severely Increased

Not Tested

Table 5: Other Diagnostic Tests Performed

CBC&

CRP Total No.

(%)

JXR Total No.

(%)

JUS Total No.

(%)

JCT Total No.

(%)

JMRI Total No.

(%)

Blood Culture Total No.

(%)

Urine Analysis Total No.

(%)

Urine Culture Total No.

(%)

Gout 65 (90.3) 44 (61.1) 38 (52.8) 3 (4.2) 1 (1.4) 17 (23.6) 53 (73.6) 14 (19.4)

P-G 7 (87.5) 7 (87.5) 7 (87.5) 0 (0) 0 (0) 2 (25) 6 (75) 1 (12.5)

SA 49 (92.5) 32 (60.4) 45 (84.9) 8 (15.1) 7 (13.2) 38 (71.7) 27 (50.9) 24 (45.3)

OA 7 (100) 5 (71.4) 5 (71.4) 1 (14.3) 0 (0) 2 (28.6) 6 (85.7) 1 (14.3)

NC-MA 23 (88.5) 12 (46.2) 8 (30.8) 3 (11.5) 2 (7.7) 8 (30.8) 14 (53.8) 6 (23.1)

12. CONCLUSIONS

1. Diseases most commonly causing MA were gout, SA and NC-MA.

2. SFIs including SFCs were not performed on a routine basis: 1/5 of patients received a SFI, 1/3 of patients a SFC. There was no SFI performed for patients diagnosed with NC-MA.

3. SFCs were only positive in 35% of patients with SA.

4. Gross appearance (colour and transparency) of SF was a reliable tool to detect inflammatory MA.

5. SF viscosity was slightly to severely decreased in 73.69% of patients diagnosed with SA and in 50% of patients diagnosed with gout.

6. Crystal detection in SF was not sensitive, only in 30% of patients diagnosed with gout MSU crystals could be identified.

7. Most patients presented with an increase of RBCs in their SF: 73.69% of patients diagnosed with SA and 60% of patients diagnosed with gout.

8. A significant (according to Table 3: Grades of Pathological SFI Changes) increase of WBC in SF of SA and gout patients was detected: 89.47% of SA patients had a moderate to severe increase, 80% of gout patients had a slight to severe increase.

9. A significant (according to Table 3: Grades of Pathological SFI Changes) increase of PMN in gout and SA patients was detected: 89.48% of SA patients had a moderate to severe increase, 70% of gout patients had a slight to severe increase.

10. Other diagnostic tests commonly used were: blood tests (CBC, CRP), JXR, JUS and UA. In SA patients BCs and UCs were often performed.

11. The results of this investigation show a discrepancy between the expected outcome and the

obtained results: SFC for diagnosing SA (see conclusion 3.) and specific crystal detection for

diagnosing gout (see conclusion 6.) were not sensitive and therefore of no big value in the

diagnosing process. However the detection of inflammatory SF (see conclusion 4.) was a

success.

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