Other
Tests
|
Test |
Description |
Normal |
Abnormal |
Diseases Association(s) |
Comments |
|
Joint aspiration |
Fluid is aspirated from
a joint. Some of this may be dripped into a sink to see if it is "stringy"
or not or whether it behaves more like water without any viscous properties.
Fluid is put into a lavender type tube for a white blood cell count
and differential. Fluid may be sent for determination of the
glucose level and protein level in the joint fluid (simultaneous blood
samples will need to be obtained to correlate with the serum values). If there is any question of infection, then
fluid will need to be sent to the laboratory for culture and gram-stain.
When crystals are suspected, fluid needs to be inspected under
a special polarizing microscope that also has a first order red compensator
present to help identify the crystals. |
Highly viscous fluid with
a WBC of less than 200 which is clear to straw colored |
Joint fluid with elevated
white cell counts up to 200-2000 are seen in noninflammatory fluid such
as in osteoarthritis. White blood
cell counts of 2000 up to 75,000 are seen in inflammatory joint fluid. Synovial fluids with white counts over 100,000
are most frequently seen with infections with septic arthritis. In this situation the culture will be positive
and the synovial fluid glucose will be more than 50 mg/100 cc less than
the blood glucose level. |
Findings of WBC counts
in the synovial fluid of up to 1000-2000 are considered noninflammatory
and are seen in diseases such as osteoarthritis.
White blood counts from 2000-75,000 are most often seen in inflammatory
arthritis such as rheumatoid arthritis, seronegative spondyloarthropathy
or crystal induced synovitis. Occasionally in crystal induced synovitis, WBCs may even go up
to 100,000 and sometimes fool the observer into thinking that the fluid
may even be infected. Generally
speaking, white blood counts in the synovial fluid of over 100,000, however,
are associated with septic arthritis with an active infection. The finding of strongly negatively birefringent
crystals under the polarizing microscope is indicative of gout with uric
acid crystals, where as weakly positively birefringent crystals are consistent
with calcium pyrophosphate crystals as seen in pseudogout |
|
| Electrical studies: (Nerve
condition velocities (NCVs), electromyo-gram (EMG) |
A physician trained in
electromyography (usually a neurologist or physiatrist) inserts needles
into the muscle and observes the electrical behavior of the muscle. The response to electrical stimuli is observed
as well as the response of the muscle to the insertion of the needle itself.
Electrical impulses are sent down the nerves and the time it takes
to travel a given distance measured. |
Normal conduction times
of impulses traveling down each nerve tested. Normal behavior of muscles electrically |
Abnormally delayed conduction
times of electrical impulses, abnormal electrical activity on muscles |
Delayed conduction of impulses
through the nerve indicating pathology in the nerve which may be due to intrinsic disease of the nerve
(neuropathy) or compression of the nerve (e.g. carpal tunnel syndrome). Abnormal electrical activity of the muscle
e.g. with low amplitude and "polyphasic" waves of electrical activity
in the muscle suggesting muscle pathology (myopathy) |
Nerve conduction studies
are done in situations where patients are complaining of numbness, tingling,
or burning in an extremity or where there are questions regarding the status
of the peripheral nerves. This test
is done to find evidence of compression of the median nerve at the wrist
(carpal tunnel syndrome) or the ulnar nerve at the elbow (cubital tunnel
syndrome). The EMG is very important
in patients who are complaining of muscle weakness and who have elevated
muscle enzymes (CPK and aldolase) where a doctor is trying to rule out the
possibility of polymyositis |