there are many forms of arthritis, there are few
laboratory investigations which are diagnostic.
Most of the investigation results only provide
some clue towards the diagnosis. It is not correct
to quickly jump to a diagnosis based on laboratory
or X-ray result only. Investigation results have
to be properly interpreted with the patient’s
clinical picture. In fact, the doctor should order
investigations based on the likely clinical diagnosis.
Routine blood test for haemoglobin and ESR is
often done and repeated in chronic cases.
blood haemoglobin depends upon nutrition (especially
iron in diet), it is often reduced by the arthritis
disease process. ESR is a measure on inflammation
or the disease process in arthritis (characterized
with painful swellings) but it does not tell us
about the exact diagnosis. ESR is often done repeatedly
to monitor the reduction in disease activity.
Rheumatoid factor is positive in blood in almost
80% of patients of rheumatoid arthritis. Another
test ASO is positive in blood in patients with
rheumatic fever arthritis. Laboratory investigations
are also done to diagnose infections (urine, stool
etc) which may lead to arthritis. Many more specialized
and expensive tests (for example ANA) are available
for some uncommon forms of arthritis (for example
SLE) and these need not be done routinely.
is no need to take X-rays of all the painful joints.
In fact, in early arthritis X-rays do not help
in diagnosis. Only in chronic or progressive arthritis
X-rays can show certain degree of damage to banes
and joints which helps in diagnosis and planning
special therapies. X-rays are also required to
plan surgery. Infrequently, arthroscopy (a viewing
tube like instrument surgically introduced into
the joint) may be done to diagnose affections
of a single large joint for example knee.