weakness, convulsions

388 Concise Book of Medical Laboratory Technology: Methods and Interpretations ¾ Latex agglutination and complement fixation tests in

cryptococcal meningitis.

SYNOVIAL FLUID (SF)

Normally, about 1 mL of SF is present in each large joint:

knee, ankle, hip, elbow, wrist, and shoulder (Table 12.3).

Clinical Indications for Aspiration

¾ Arthritis of unknown etiology, manifested by effusion.

¾ Possible infectious arthritis, with or without effusion, to

obtain material for culture.

¾ Effusions of known etiology, to relieve pain or to allow

mobility.

Aspiration must be done under absolute aseptic

conditions. Since effusion often exists when aspiration is

indicated, 10–20 mL of fluid may usually be obtained. The

specimen is collected in 3 to 4 sterile tubes.

1. Plain tube for gross examination, evaluation of viscosity,

and mucin clot test.

2. EDTA tube for cell counts and microscopic study.

3. A sterile, plain or preferably heparinized tube (precludes

clot formation) for microbiologic study.

4. Appropriate tube(s) for serologic or chemical examinations: Plain tube for serologic tests or enzyme assays,

heparinized tube for total protein, oxalate fluoride

tube for glucose.

Viscosity

When normal fluid drips from a syringe, a tenacious ‘string’

at least 4 cm long forms with each drop. This provides an

estimate of whether viscosity is normal, decreased (string

less than 4 cm in length), or markedly decreased (string

less than 1 cm in length).

Another method for evaluating viscosity is to see how

far a drop of fluid can be stretched between the thumb and

index finger before breaking: fluids with very low viscosity

will behave like water. Decreased viscosity reflects

decreased hyaluronate in the synovial fluid.

Mucin Clot Test (Ropes’ Test)

This is done by adding 1 mL of synovial fluid to 20 mL of 5%

(v/v) acetic acid in a small breaker. Normally, a compact

TABLE 12.2: Grades of syphilitic spinal fluid

Investigation Grade I Grade II Grade III

Serology — ± ++

Number of WBCs/cu mm 5–25 25–100 70–100

Protein increase + ++ +++

Colloidal gold curve 0000000000 0023454310 5555554310

TABLE 12.3: Presence of synovial fluid

Synovial fluid Findings SI units

parameter

Appearance Clear or colorless to pale

yellow

Crystals Absent

Glucose

Transudate < 10 mg/dL lower than blood

glucose (whole blood adult

normal 60–89 mg/dL, child

norm 51–85 mg/dL)

Exudate Lower than whole blood

levels

Lactate dehydrogenase

Transudate < Client’s serum LD

(serum adult normal

45–90 U/L, child normal

60–170 U/L)

Exudate > Client’s serum LD

pH 7.4

Specific gravity

Transudate < 1.016 < 1.016

Exudate > 1.016 > 1.016

Total protein

Transudate 1–3 g/dL 10–30 g/L

Exudate > 3 g/dL > 30 g/L

Volume < 4 mL

Viscosity High

White blood cells

Transudate < 100/mm3 < 100 × 109

/L

Exudate > 1000/mm3 > 1000 × 109

/L

Cerebrospinal and Other Body Fluids 389

large clot will form, surrounded by clear solution, this is

graded as ‘good’. If a soft clot forms in a turbid solution,

this is graded as fair. A friable clot with cloudy surrounding

fluid is graded as ‘poor’ or ‘fragile’. No clot formation, with

flakes in a cloudy suspension, is graded as ‘very poor’.

Good clots do not break up when agitated, while poor clots

break up into small shreds. This procedure actually is an

estimate of synovial hyaluronate and not mucin, which is

absent in joint fluid.

Microscopic Examination

Total and differential counts as for CSF. But the usual

leukocyte diluent with 1% glacial acetic acid precipitates

synovial fluid hyaluronate and is unsatisfactory, instead

methylene blue in saline can be used. If the fluid is very

turbid, use saline dilution or digestion with hyaluronidase

(2 mL SF incubated with 150 IU hyaluronidase for 1 hour at

37oC) may be helpful. Differential count can be done from

EDTA sample (sediment) that has been centrifuged, a film

made and stained as for peripheral blood.

LE cells are frequently seen in stained SF from patients

with systemic lupus erythematosus (SLE). Sometimes,

they can be seen in cases of rheumatoid arthritis. Large

phagocytes containing neutrophils may be found in SF

and are called ‘Reiter cells’, they are nonspecific and

may be present in effusions of varying etiology. RA cells

or ‘Ragocytes’ are neutrophils containing 0.5 µ to 1.5 µ

inclusions better seen with phase contrast microscopy.

They are seen in 94% cases of rheumatoid joint fluids

but are nonspecific for they can also be found in septic

arthritis, gout, etc.

Both wet preparation (a drop of SF put on a slide and

coverslipped) and stained films should be studied for

crystals, using polarized light to detect monosodium urate

(MSU) or calcium pyrophosphate dihydrate (CPPD). MSU

crystals appear birefringent and needle or rod shaped;

while CPPD crystals will appear birefringent and rhomboid

or rod shaped. MSU crystals are found in acute/chronic

gout joints. CPPD crystals are found in pseudogout or

chondrocalcinosis.

Immunologic Studies

Seronegative rheumatoid arthritis may have a positive

joint fluid, but this is not very specific. Decreased synovial

fluid complement (under 30% of serum level) occurs in

rheumatoid arthritis and SLE (Table 12.4).

PLEURAL FLUID

The pleural surfaces are normally moistened by 1 to 10 mL

of fluid derived by ultrafiltration of plasma. Normal protein

concentration of this fluid is 1–2 g% with no fibrinogen

(Table 12.5).

Appearance Viscosity White cells Mucin clot Protein total (Avg-g%)

Globulin

Remarks

Normal Straw-colored, High 200–600/25% poly’s Good 1.36 0.05

clear, cloudy

Traumatic Yellow to bloody High ± 2000/30% poly’s Good 4.27

Osteoarthritis Yellow, clear High ± 1000/20% poly’s Good 3.08 0.75 Cartilage fibrils

Rheumatic Yellow, slightly

cloudy

Low ± 10,000/50% poly’s Good 3.74 1.07

Systemic lupus Straw-colored, High ± 5000/10% poly’s Good

erythematosus slightly cloudy

Gout Yellow to milky

cloudy

Low ± 12,000/60% poly’s Fragile 4.18 1.54 Urate

crystals

Tuberculous Yellow, cloudy Low ± 25,000 Fragile 5.3 2.0 Tubercle

arthritis 50–60% poly’s bacilli

Septic arthritis Grayish or bloody, Low ± 80,000/90% poly’s Fragile 5.64 2.45 Bacteria

turbid

Rheumatoid Yellow to greenish, Low ± 15,000 Fragile 4.74 1.79 Rheumatoid

arthritis cloudy 65% ± poly’s factor

TABLE 12.4: Synovial analysis in arthritis

390 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 12.5: Presence of pleural fluid

Pleural fluid Observation SI units parameter

Appearance Clear, slightly amber

Cholesterol

Transudate < 60 mg/dL < 1. 55 mmol/L

Exsudate > 60 mg/dL > 1. 55 mmol/L

Glucose

Transudate Approximates whole

blood levels (whole

blood adult normal

60–89 mg/dL, child

normal 51–85 mg/dL)

Exudate Lower than whole

blood levels