Examination of Synovial Fluid as a Diagnostic Aid in Arthritis

Examination of Synovial Fluid as a Diagnostic Aid in Arthritis JOSEPH LEE HOLLANDER, M.D., F.A.C.P.* ANTONIO REGINATO, M.D.** TITO P. TORRALBA, M.D.***

Fairly extensive knowledge of the characteristics of synovial fluid has been available for at least the past 30 years, and a monograph on the subject by Kling appeared in 1938. 9 Ropes and Bauer published a classic monograph on their extensive studies and findings in 1953. 16 Since many of the newer discoveries which have increased the diagnostic importance of synovial fluid examination in the differentiation of various forms of arthritis have emanated from the Arthritis Section of the Department of Medicine of the Hospital of the University of Pennsylvania during the Chairmanship of Dr. Francis C. Wood, it is appropriate to review these newer findings here. Specific laboratory tests for the diagnosis of various forms of arthritis are usually lacking. The tests for rheumatoid factor in serum may be helpful in establishing the diagnosis of rheumatoid arthritis, but are often negative in early cases when diagnostic aid is most needed. Likewise, the L.E. phenomenon is helpful in diagnosis of systemic lupus erythematosus, but is often negative in the early stages or between severe exacerbations of the disease. The serum uric acid determination may help to establish the diagnosis of gout, but may be normal in early disease, or may be falsely elevated in various conditions, as in patients taking thiazide diuretics. Bacterial cultures have long been utilized for diagnosis of septic arthritis. Many of the other forms of arthritis have heretofore been diagnosed on

* Professor of Medicine, School of Medicine, University of Pennsylvania; Chief, Arthritis

Section, Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia ** Fellow in Medicine (Rheumatology), Hospital of the University of Pensylvania *** Fellow in Medicine (Rheumatology), Hospital of the University of Pennsylvania

1281

1282

JOSEPH LEE HOLLANDER, ANTONIO REGINATO, TITO

P.

TORRALBA

clinical findings alone. X-ray changes are diagnostic only in late disease, and synovial biopsy studies are usually difficult to obtain and the results frequently are nonspecific. In the past it had been usual that aspirated synovial fluid from a joint effusion would be sent to the laboratory for culture but no other studies made upon it. The findings of Ropes and Bauer 16 and others had been frequently ignored or never learned. It has become increasingly clear during the past ten years, however, that synovial fluid analysis is both the most valuable and yet the most neglected differential diagnostic test for arthritis. 3 Further studies of synovial fluid have also revealed new facts concerning the pathogenetic mechanisms of the diseases involved. Study of synovial fluid has presented a virtually unexplored frontier in the investigation of arthritis. ASPIRATION OF SYNOVIAL FLUID

Most physicians have received little or no experience in the aspiration of effused joints. This can be readily corrected by review of an anatomical atlas showing the details of each joint to be aspirated. Complete directions with all details for the aspiration of most joints are available elsewhere,2 so only a brief summary will be presented here. A strictly aseptic technique is important to prevent joint infection from the procedure, but this need not include use of drapes and gloves. The area over the joint to be aspirated is thoroughly cleansed with an antiseptic detergent (e.g., pHisoHex), and the skin is then painted with tincture of iodine or another antiseptic accepted by surgeons for skin preparation. This is allowed to dry, and the excess may be removed with alcohol sponges. Infiltration of the skin and deeper tissues with procaine solution is seldom needed, but a brief spraying of the site with ethyl chloride is usually adequate to prevent excessive pain from the needle puncture. Disposable needles and syringes, now becoming standard equipment in many hospitals and clinics, have reduced the danger of infection greatly. If regular needles and glass syringes are to be used, they should be thoroughly washed and adequately autoclaved to insure sterility. Needles of smaller gauge than 20 are usually not adequate for aspiration of the thick or viscous fluid in a joint. The knee is by far the most often tapped joint. With the patient lying supine, the needle is inserted into a site medial to the patella so that it enters the fully extended and relaxed joint posterior to the patellar margin. This will make it possible to aspirate some fluid from practically any painful knee if the synovial cavity has been punctured. All available fluid is withdrawn at aspiration, but even a few drops can yield valuable diagnostic information. Fluid can also be obtained by aspiration from hips, shoulders, ankles, elbows and even smaller joints or bursae when there is effusion.

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1283

TECHNIQUE OF SYNOVIANALYSIS

Paracelsus termed joint fluid synovia since it grossly resembles eggwhite. At present it is usually called synovial fluid, but the shortening of the term synovial fluid analysis into synovianalysis has been accepted. 4 Whenever possible, specimens should be examined fresh. Heparinized tubes are useful to prevent fibrin clotting. Specimens may be preserved intact for long periods if kept frozen. 1

Gross Appearance Although it may seem obvious, it is important to note the color, consistency and clarity of the fluid as this varies tremendously among the different types of arthritis, as well as with the severity of each. Normal joint fluid is straw-colored or lighter, with deeper yellow or even xanthochromic fluids resulting from accumulation of blood pigment. Blood may be present in gross amounts, either from trauma or from overuse of an inflamed joint. If the fluid is homogeneously bloody, hemarthrosis is present. Bloody streaking in the aspirated fluid denotes puncture of a synovial vessel by the aspirating needle. Fluid from active rheumatoid arthritic joints may appear yellow, greenish or even orange; that from a tophaceous gouty joint may appear yellow to milky white. Purulent joint fluid often has a grayish appearance, or may look brown when containing blood as well. The clarity or turbidity of the fluid is also variable, depending on the amount of suspended material, be it cellular, crystalline, or debris including cartilage fragments or fibrin. Usually, the cloudier the fluid, the higher the cell count.

Viscosity Although, for careful investigative work, an Ostwald viscometer may be necessary for quantitative comparative viscosity of synovial fluid, extensive experience has shown that the viscosity may be estimated accurately enough for clinical use by a simple "string test." This may be carried out by allowing the fluid to drip, drop by drop, from the syringe or a pipette into the sink Ca real sink test with value). The length of the string formed by each drop before it separates gives a relatively accurate quantitation. Normal or osteoarthritic fluids, unless diluted by a recent marked increase in volume by transudation from plasma, string out more than 3 cm. before separating. Fluid from active rheumatoid arthritis, acute gout or various types of septic arthritis will drip with little or no stringing. When the amount of fluid obtained is small, a drop may be placed on the thumb, touched with the index finger, and a string forms as the fingers are separated. If the string breaks before reaching a length of 3 cm. the viscosity of the fluid is lower than normal.

Mucin Clot The protein-polysaccharide complex, or protein-hyaluronate, of sy-

1284

JOSEPH LEE HOLLANDER, ANTONIO REGINATO, TITO

P.

TORRALBA

novial fluid (mucin) coagulates on acidification. The addition of a drop or two of synovial fluid to a few miIIiliters of 5 per cent acetic acid in a beaker forms a small clot which is allowed to stand for one minute. If the hyaluronate complex is of normal character, the clot is firm and does not separate or shred on shaking the beaker. IQ In active inflammatory conditions, such as rheumatoid arthritis, the polymerization of the hyaluronate is decreased and the clot is friable even to the point of fragmenting completely and leaving a somewhat cloudy solution. Because both viscosity and clot are dependent on the character of the hyaluronate, it is usual that fluids with poor viscosity also form poor mucin clots. The main exception to this is in effusions from recent inflammation, trauma or overuse in which the viscosity has been decreased by dilution with plasma dialysate. In such instances the quality of the clot may remain normal.

Cytology The acid fluid used for ordinary white cell counting is unsatisfactory for synovial fluid cell counts because it coagulates the mucin in the pipette, yielding inaccurate counts. Red cell counting fluid (Hayem's solution) may be used, or isotonic saline solution. If red cells are present in large numbers they may be counted separately. The counting chamber is filled from the pipette after proper dilution. Counting of leukocytes is performed with high-dry power, so that red cells are recognized and excluded on sight or counted separately. The counting is identical to that for the leukocyte count on blood. Differential counts of leukocytes may be made from examination of a smear stained by the standard Wright's stain technique. For the best smears, the fluid is centrifuged, the supernatant fluid removed, the cellular sediment washed by redilution to original volume with isotonic saline, and centrifuged again to remove most of the mucin. The sediment is then easily smeared on the slide, dried, fixed and stained in the standard way.

Tests for Rheumatoid Factor Synovial fluid may often contain rheumatoid factor in early rheumatoid arthritis before it is detectable in significant amount in serum. Even in active rheumatoid arthritis the titer may differ significantly from that of serum. 15 Routine determination of the synovial fluid rheumatoid factor concentration is, therefore, often of value. The fluid, either whole or supernatant from centrifugation, is tested the same as serum by any of the standard techniques. The most frequently used technique has been the latex agglutination reaction, either the Hyland slide technique or the more precise tube method of Singer and PlotzP Positive tests are those which show agglutination in a dilution of 1 :80 or more in our experience, but even lower titers may be suggestive and helpful in differential diagnosis.

Bacterial Culture Any synovial fluid specimen having a high white cell count, particularly

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1285

if noted for the first time, is best sent to the bacteriology laboratory for routine culture. Acid-fast stain of sediment may be obtained from synovial fluid sediment whenever tuberculous arthritis might be suspected, and culture for tubercle bacilli may also be ordered. Cultures are useful especially when a joint is aspirated which had been previously injected with corticosteroid elsewhere, because low-grade chronic infection occasionally may result from inadequate aseptic precautions at the time of previous joint aspiration and injection. Special cultures, such as those for viral or mycoplasmal organisms, may occasionally be indicated.

Microscopic Examination The simple examination of a drop of fresh, uncentrifuged synovial fluid has revealed more new information on the differential diagnosis of arthritis than any other test upon it in our experience over the past 10 years. A drop of fluid is placed on a clean slide, is covered with a cover slip, and the edges may be sealed with petroleum jelly or clear nail polish to prevent drying. Such preparations, viewed under the microscope, have yielded definitive information on rheumatoid arthritis, osteoarthritis and gout, and have led to the discovery of pseudogout as a hitherto unrecognized form of joint disease. Under low power a rough estimate of cells can be made, and other particulate matter noted which can be further studied under higher magnification or under phase-contrast or polarized light. Even the ordinary microscope can be easily and cheaply adapted for polarized light viewing by insertion of polaroid discs into the condenser and eyepiece. For polarized light viewing, the eyepiece is then rotated until the darkest position is reached. Phase-contrast condensers are available, but for most purposes simply lowering the position of the condenser somewhat will bring out detail in particulate matter. Using ordinary light and high-dry (X450) magnification the white cells can be studied for presence of cytoplasmic inclusion granules which are so common in rheumatoid arthritis and its variants, but may also be seen in gouty, septic (motile bacteria may occasionally be visible in the wet preparation) or other inflammatory forms of arthritis as they are particles of phagocytosed material of various types. Our finding of these cells and identification of the material in the cytoplasmic granules has opened a new approach to the study of rheumatoid arthritis, and is described elsewhere. 5 , 13, 14 Supravital stains of such cells may be prepared by adding a small drop of Sternheimer-Malbin stain to a drop of synovial fluid on a slide, mixing with a wire loop, and adding a cover slip.s One soon becomes accustomed to the morphological differences between red cells, lymphocytes, polymorphonuclear leukocytes, and macrophages in these wet preparations. It is important to keep in mind that one is looking at spherical cells, rather than the flattened cells seen on stained smears, however.

1286

JOSEPH LEE HOLLANDER, ANTONIO REGINATO, TITO

P.

TORRALBA

The irregular shape of stippled-appearing particles of varying size, usually in a fluid containing few cells, identifies cartilage fragments. These particles, originally described by US,4 are characteristic of osteoarthritis. A "cartilage fragment count" can be made by estimation of the number of fragments per high-power field. This is an index of the rate of degeneration of the involved joint, i.e., the greater the number of fragments (and the greater the size) the more rapidly the joint cartilage is being broken down by use. In addition to cartilage fragments, numerous fine, short, threadlike particles may be seen, even under low power, in such fluids. These differ from the strands and webs of fibrin particularly by their very short length, and are probably cartilage reticulum (collagen) fibrils, remaining after autolysis of their surrounding cartilage matrix by action of synovial fluid enzymes or phagocytic lysosomal enzymes. Positive identification of such fibrils as collagen by means of electron-microscopic study is in progress. Two types of crystals have so-far been identified in human synovial fluids. (However, recently injected corticosteroid, also crystalline, might confuse the unwary.) In gouty synovial fluid the crystals of monosodium urate are found in almost 100 per cent of specimens if polarized light is used. These needle-like crystals, which may be broken into small pieces by the mortar-and-pestle-like action of the joint surfaces, can be seen as black particles under ordinary light, but shine out distinctly as bright needles against the dark background under polarized light. Use of a first order red plate compensator in the polarized light microscope shows such crystals to be strongly and negatively birefringent, i.e., yellow when parallel to the plane of the compensator, blue when at right angles to the plane of the compensator, against the red background of the field. Such crystals may be found floating free in the fluid from chronic gouty joints, but mostly have been phagocytosed and appear in the cytoplasm of neutrophils in fluid from acute gouty joints. The identification of these crystals as a pathognomonic or diagnostic finding in gout originated in our laboratory.1 1 McCarty, while working in our laboratory, also noticed another type of crystal appearing in synovial fluid of nongouty patients. Although such an occurrence was relatively rare in incidence, he later identified such rodlike or short crystals as a form of calcium pyrophosphate deposited in cartilage or joint fluid of more than 30 patients, many of whom suffered recurrent attacks of acute arthritis.lO, 12 This condition had been clinically described by others19 shortly before McCarty's report, but based only on the x-ray appearance of calcium deposits in articular cartilages, hence was termed "articular chondrocalcinosis."19 No synovial fluid studies were made by these workers. Calcium pyrophosphate crystals, as opposed to urate crystals, are weakly and positively birefringent when viewed under compensated polarized light, i.e., are weakly blue when parallel to the plane of the compensator, and weakly yellow at right angles to it. These crystals of pseudogout

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1287

may be seen floating free, as phagocytosed particles in the leukocytes, or in the cartilage fragments of joint fluid. At times this condition would appear to develop as a late complication of osteoarthritis, perhaps because of the attrition of exposed articular bone ends with resultant accumulation and re crystallization of bone salts in fluid and remaining articular cartilage. FINDINGS IN SPECIFIC TYPES OF ARTHRITIS

The findings from synovial fluid analysis for some of the forms of arthritis are summarized in Table 1. Even a casual scanning of this table will show the marked differences which can aid in differentiating various types. Normal synovial fluid, of course, is rarely examined, but a discussion of special features of the fluid in various types of arthritis follows.

Traumatic Arthritis Fluid from traumatized joints shows variable concentrations of blood. The viscosity and clot are good unless the amount of bleeding dilutes the synovial mucin greatly. The proportion of white cells to red cells in such fluid is little different from whole blood. If damage has continued, there may be cartilage fragments visible. Similar findings, with massive hemarthrosis, are noted in fluid from villonodular synovitis or hemophilic arthritis.

Osteoarthritis This prevalent joint condition in middle-aged or older persons does not produce massive joint effusions except under conditions of marked overuse. The fluid is usually so clear that print can be read through the syringe or tube containing it. As the condition progresses the clarity may decrease, and small white particles may be noted suspended in it (cartilage fragments). Viscosity and clot are good, and the cell count is rarely over 1000 WBe/cu. mm., with a differential count of up to 20 per cent neutrophils, usually 50 per cent lymphocytes, and the balance mononuclear phagocytes or synovial lining cells. The striking feature of such fluid, described above under Microscopic Examination, is the presence of few to many cartilage fragments and fibrils. This is not surprising when one considers the nature of the disease. Long ago "cartilage shredding" was described by some Norwegian workers who were studying sections of articular cartilage from osteoarthritis. The desquamated shreds of cartilage apparently remain viable and are suspended in the fluid for relatively long periods. Macroscopic fragments of cartilage may be large enough to be called "joint mice" and may produce damage to the joint by catching between articulating surfaces.

Charcot's Arthropathy The findings in the joint fluid of this neurogenic joint disease are

Good Poor

Yellow, slightly cloudy Low

Yellow, slightly cloudy Normal

Yellow, cloudy

Yellow, slight- Normal ly cloudy or low

Yellow to greenish, cloudy

Yellow, cloudy

Grayish to bloody, turbid

Rheumatic fever

Systemic Lupus Erythematosus

Gouty Arthritis

Pseudogout

Rheumatoid Arthritis and Variants

Tuberculous Arthritis

Septic Arthritis

Low

Low

Low

Low

Fair

Normal

Yellow, clear

Osteoarthritis

Poor

Poor

Poor

Good

Good

Good

Normal

Cloudy, bloody

Good

MUCIN CLOT

Traumatic Arthritis

High (normal)

VISCOSITY

Straw, clear

APPEARANCE

Normal

DISEASE

80,000"= 90% PMN

25,000"= 40-50% PMN

8,000 to 40,000 70% PMN

6,000+ 75%PMN

°

°

Rare (cholesterol)

Few to many (Ca pyrophosphate)

Many (urate)

0

3,000'!: lO%PMN 10,000+ 75%PMN

0

10,000"= 50% PMN

0

0

2,000"= (many RBC) 1,000"= 20%PMN

0

CRYSTALS

200-600 25% PMN

WHITE CELL COUNT

Table 1. Synovianalysis in Arthritis

°

0

°

°many to

°

0

Latex neg.; culture, + Inclusion body cells negative for rheumatoid factor J)ecreased glucose

Glucose low; Latex neg. Acid-fast bacterial culture, +

5-95% of PMN show inclusions Latex positive

Crystals in cells, free, or in cartilage fragments (weakly positive birefringence)

Crystals in cells or free negative birefringence.

L.E. cells on smear

Few inclusion body cells

0

fragments, fibrils 0

0

0

SPECIAL FEATURES

+

o or

0

CARTILAGE DEBRIS

I>

~

~

~

~

~~

~ Q

o

iat

i'j

j'J

~

g:

i'j

t"' i'j

~

i'j

2;' 1:J]

""'"

~

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1289

similar to those of severe osteoarthritis,16 but with large and numerous cartilage fragments, and xanthochromic fluid or even gross hemarthrosis. Rheumatic Fever

Few examinations of the joint fluid of this relatively benign and transitory form of joint disease have been reported. Ropes and Bauer 16 found the fluid slightly cloudy, the viscosity lowered, but the mucin clot good, with cell counts of about 10,000 WBC/cu. mm., and about half of these were polymorphonuclear leukocytes. In the only joint fluid from a patient with acute rheumatic fever we have obtained for study, such findings were confirmed, with one important addition. Nearly half of the neutrophils showed cytoplasmic inclusion granules. By immunofluorescent staining techniques as previously described by Rawson, Abelson and Hollander,13 such inclusion granules contained gamma globulin and macroglobulin with complement. This confirms the antigen-antibody nature of the joint involvement of rheumatic fever and demonstrates as well the similarity of the process to that of rheumatoid arthritis (see below). Systemic Lupus Erythematosus

Ropes and Bauer 16 carefully and accurately described the chemical and cytological features of the joint fluid obtained from inflamed joints of patients with systemic lupus erythematosus. The viscosity and clot is usually normal in this condition, and the leukocyte count is rarely mm:e than 3000 per cu. mm. with a differential count showing nearly 90 per cent of mononuclear cells, mainly lymphocytes, and about 10 per cent neutrophils. To this we have added two important findings. In wet preparations of such fluids we have found cytoplasmic inclusion granules which can be stained specifically for gamma globulin but not macroglobulin by immunofluorescent techniques. Feulgen-stained smears of such cells demonstrate the presence of DNA in the granules. More important, from the standpoint of the clinician, Wright's stained smears of the cells, prepared as described under Differential Counts above, nearly always show numerous L.E. cells of typical morphology. This provides a "spot diagnostic test," because only a few minutes are required to centrifuge the freshly obtained fluid, smear the sediment and stain the slide for immediate examination. This was discovered first in examination of pericardial fluid from a patient in her first acute attack of systemic lupus,7 and has since been confirmed by examinations of pleural fluid and joint fluid whenever available for aspiration. No incubation techniques, heparinization, etc. are required as the "incubation" has already taken place in vivo in whichever serous or synovial cavity is involved. The formation of L.E. cells has always been described previously as a "post-vital" phenomenon, but some have argued that such inflamed cavities are actually not part of the body-proper. Whether or not they are, fluid from joints or serous cavities provide a quick source for L.E. cells when rapid diagnosis of such

1290

JOSEPH LEE HOLLANDER, ANTONIO REGINATO, TITO

P.

TORRALBA

an acute inflammatory process may be lifesaving by suggesting immediate corticosteroid therapy.

Gouty Arthritis Our original demonstrationll of urate crystals in gouty synovial fluids, referred to above, has now been widely confirmed and accepted as the most specific laboratory test for diagnosis.1 8 • 20 The synovial fluid may appear grossly similar to that of rheumatoid arthritis, the viscosity and clot may likewise be poor as in the latter disease, and the cell count and differential count may also be remarkably similar. Some of the cells from a few gouty fluids, in addition to those showing phagocytosed crystals, have contained cytoplasmic inclusions which appeared similar to those from rheumatoid arthritic fluids, and have even stained by fluorescent techniques for gamma globulin and macroglobulin. Whether this represents concomitant gout and rheumatoid arthritis in such instances has not yet been determined. Identification of urate crystals has been described above, under Microscopic Examination. Pseudogout Fluids from joints inflamed from calcium pyrophosphate deposition may appear similar to those of gout or rheumatoid arthritis by all tests except polarized light microscopy. Identification of the weakly positive birefringent crystals 10 has also been described above. Rheumatoid Arthritis Ropes and Bauer16 made an excellent and complete study of fluid characteristics in rheumatoid arthritis except for two important facts which were added later. We have confirmed the findings of various workers that the tests for rheumatoid factor often become positive in joint fluid earlier and in more patients than such tests on serum. This was elaborated earlier in this account. Occasionally, cholesterol crystals may be found in rheumatoid arthritis fluids, particularly in very chronic effusions. Our main contribution to the study of the synovial fluid in rheumatoid arthritis has been the description and characterization of the cytoplasmic granules in the phagocytes (Fig. 1). Such cells, if the nature of the inclusion has been determined either by release of rheumatoid factor as a result of a cell-macerating technique, 5 or by fluorescent staining for gamma globulinrheumatoid factor complex, 13 may be properly called "R.A. cells." These are completely analogous to the L.E. cells of systemic lupus erythematosus, but are not specific on morphological or staining characteristics alone. Such inclusion-bearing leukocytes constitute from 5 to 95 per cent of the totalleukocyte population of rheumatoid synovial fluid., In less than 5 per cent.ofmore than.600 specimens of rheumatoid fluid such. cells were not seen~ Thechal'acterization of the cells has led to aJlew hypothesis of the pathogenesis of rheumatoid arthritis, 5 which .hasb(jen supp()rtedby many diverse findings by US14 and by others subsequently. .

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1291

Figure 1. Polymorphonuclear leukocytes containing typical cytoplasmic inclusions in wet preparation of synovial fluid of rheumatoid arthritis. A, Original magnIfication X450. E, Original magnification X1200. (Microphotographs by George B. Backer, M.D.).

Variants of Rheumatoid Arthritis Although psoriatic arthritis, juvenile rheumatoid arthritis, ankylosing spondylitis, the arthritis of ulcerative colitis and arthritis with agammaglobulinemia differ in many clinical characteristics from classical rheumatoid arthritis, our findings on synovial fluid from these "rheumatoid variants" show no significant difference from rheumatoid arthritis. Although the rheumatoid factor tests are usually negative in serum from such patients, they are usually positive, at least in low titer, in joint fluid. "R.A. cells" have been identified in most of these variants. 5 • 13 In a very recent study of synovial fluid from the arthritic knee of a patient with complete agammaglobulinemia as determined by both paper and immunoelectrophoresis, we found "R.A. cells" with cytoplasmic granules which stained for gamma globulin by fluorescein-Iabeled antigamma globulin serum. Furthermore, immunoelectrophoresis of the joint fluid showed a faint, but definite, line in the typical position for macroglobulin. Tests for rheumatoid factor by the latex method were negative on fluid and the untrasonicated cells, however. Thus, both gamma globulin and macroglobulin have been demonstrated at the site of inflammation, even though absent in the circulation. These findings and their implications will be fully described elsewhere. 6 Although firm conclusions are as yet premature, we have felt the findings on the fluids from "rheumatoid variants" indicate that they are indeed clinical variants of the disease. Others, however, feel these results might indicate that rheumatoid factor is not specific for rheumatoid arthritis. At least we have evidence that would suggest that all are similar antigenantibody induced (autoimmune) diseases.

Septic Arthritis Characteristics of septic joint fluids have been thoroughly studied and

1292

JOSEPH LI,E HOLLANDER, ANTONIO REGINATO, TITO

P.

TORRALBA

described by Ropes and Bauerl6 and are summarized in the table. Markedly lowered glucose levels in joint fluid, as compared with blood levels, are highly significant. Most important, of course, is suspicion of the nature of the disorder and prompt culture of the fluid on appropriate media so that suitable antibiotic therapy may be carried out promptly and intensively. Inclusion body cells are often found in septic joint fluids, but they have not shown presence of rheumatoid factor-gamma globulin complexes in the granules. 13 Latex tests for rheumatoid factor on such fluids have been negative. SUMMARY AND CONCLUSIONS

From a wide experience with synovianalysis we have concluded that careful examination of joint fluid is the most definitive diagnostic laboratory test for differentiation of the various forms of arthritis. It is also the diagnostic aid least frequently utilized by physicians. Study of the joint fluid is as important in arthritis as urinalysis in renal disease. Synovial fluid is actually a "liquid biopsy" from the site of inflammation. Many new facts about arthritis are being added to our knowledge each year from studies on the synovial fluid. Some of these advances have been described in this report, together with a detailed description of techniques and findings in various forms of arthritis. REFERENCES 1. Backer, G. B., Rodriguez, C. E. and Koehl, C. W.: Microscopic evaluation of frozen synovial fluid. Arth. & Rheum. 8: 429, 1965. 2. Hollander, J. L.: Intrasynovial steroid therapy. Chapter 24 in Arthritis and Allied Conditions (J. L. Hollander, Ed.)., 7th Ed., Philadelphia, Lea & Febiger, 1966. 3. Hollander, J. L.: The most neglected differential diagnostic test in arthritis. Arth. & Rheum. 3: 364, 1960. 4. Hollander, J. L., Jessar, R. A. and McCarty, D. J.: Synovianalysis: An aid in arthritis diagnosis. Bull. Rheum. Dis. 12: 263, 1961. 5. Hollander, J. L., McCarty, D. J., Astorga, G. and Castro-Murillo, E.: Studies on the pathogenesis of rheumatoid joint inflammation. 1. The "R.A. cell" and a working hypothesis. Ann. Intern. Med. 62: 271, 1965. 6. Hollander, J. L., Rawson, A. J., Abelson, N. M., Torralba, T. and Reginato, A.: Immune globulins in synovial fluid from arthritis with agammaglobulinemia. Arth. & Rheum. 9: June, 1966. Presented at Annual Meeting, Am. Rheumatism Assoc., Denver, Colorado, June 18, 1966. 7. Hollander, J. L. and Viner, E.: Unpublished data. 8. Jessar, R. A.: The synovial fluid. Chapter 5 in Arthritis and Allied Conditions (J. L. Hollander, Ed.), 7th Ed., Philadelphia, Lea & Febiger, 1966. 9. Kling, D. H.: The Synovial Membrane and Synovial Fluid. Los Angeles, Los Angeles Medical Press, 1938. 10. McCarty, D. J., Jr.; Pseudogout. Chapter 56 in Arthritis and Allied Conditions (J. L. Hollander, Ed.), 7th Ed., Philadelphia, Lea & Febiger, 1966. 11. McCarty, D. J., Jr. and Hollander, J. L.: Identification of urate crystals in gouty synovial fluid. Ann. Intern. Med. 54: 452, 1961.

EXAMINATION OF SYNOVIAL FLUID AS A DIAGNOSTIC AID IN ARTHRITIS

1293

12. McCarty, D. J., .Jr., Kohn, N. N. and Faires, J. S.: The pseudogout syndrome. Ann. Intern. Med. 56: 711, 1962. 13. Rawson, A. J., Abelson, N. M. and Hollander, J. L.: Studies on the pathogenesis of rheumatoid joint inflammation. H. Intracellular particulate complexes in rheumatoid synovial fluids. Ann. Intern. Med. 62: 281, 1965. 14. Restifo, R. A., Lussier, A. J., Rawson, R. A., Rockey, J. H. and Hollander, J. L.: Studies on the pathogenesis of rheumatoid joint inflammation. Ill. The experimental production of arthritis by the intra-articular injection of purified 7S gamma globulin. Ann. Intern. Med. 62: 285, 1965. 15. Rodnan, G. P., Eisenbeis, C. H. and Creighton, A. S.: On the occurrence of rheumatoid factor in synovial fluid. Arth. & Rheum. 5: 316, 1962. 16. Ropes, M. W. and Bauer, W.: Synovial Fluid Changes in Joint Disease. Cambridge, Mass., Harvard University Press, 1953. 17. Singer, J. M. and Plotz, C. M.: Latex fixation test in the serological diagnosis of rheumatoid art.hritis. Am. J. Med. 21: 888, 1956. 18. Wyngaarden, J. B.: Etiology and pathogenesis of gout. Chapter 54 in Arthritis and Allied Conditions (J. L. Hollander, Ed.), 7th Ed., Philadelphia, Lea & Febiger, 1966. 19. Zitnam, D. and Sitaj, S.: Chondrocalcinosis articularis, a clinical and radiological study. Ann. Rheum. Dis. 22: 142, 1963. 20. Zvaifler, N. J. and Pekin, T. J.: A.M.A. Arch. Intern. Med. 111: 99,1964. 206 Maloney Building Hospital of the University of Pennsylvania Philadelphia, Pennsylvania 19104