Though 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.

           Though 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.

          There 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.