Rheumatoid Arthritis: Early Diagnosis is key – role of antibodies and Musculoskeletal Ultrasound
Rheumatoid factor (RF) in Rheumatoid Arthritis (RA) was first discovered in 1940.
Until 1940s RA was only a clinical disease and early inflammatory arthritis could not be diagnosed.
Anti CCP IN RA
Anti CCP antibodies were discovered in 1964. Until then RA negative for RF but positive for CCP was easily missed. In this paper Table 2 shows the sensitivity of RF and CCP in early RA and their combined sensitivity is 30 to 40 % only.
“The low sensitivity of the test (40–50% in most published cohorts) indicates that a negative anti-CCP antibody test does not exclude disease, but its high specificity means that a positive result markedly increases the probability that the patient will have RA. “
“A significant number of these patients do not have rheumatoid factor, and may not otherwise have been expected to develop severe aggressive disease. “
This paper shows the evolutionary history of RA. This is highly typical for all autoimmune diseases. Clinical syndrome is progressively defined based on cumulative signs and symptoms and response to treatment. This is often followed by pathological evidence such as the discovery of various antibodies or Histopathology. The rapid evolution of such immunological tests coupled recently with a large number of genetic findings has been changing the diagnostic criteria (lupus is prime example).
Role of Musculoskeletal Ultrasound (MSKUS) in RA diagnosis
It has been shown that with MSKUS the diagnostic certainty for inflammatory arthritis increased from 33% (clinical only) to 72% (P <0.001). “With regard to a diagnosis of RA, the proportions were 31.1% pre-test and 61.2% post-test (P <0.001). MSKUS findings agreed with the final diagnosis in 95% of patients. “
A recent study showed that erosions (joint damage) developed in feet and was detectable by MSKUS in RA patients that had no clinical synovitis but were positive for anti-CCP antibodies. Hence, MSKUS is an extremely useful tool for detecting early inflammatory arthritis.
Seronegative RA if missed can lead to severe consequences similar to seropositive disease. In seronegative RA even RF and anti-CCP antibodies are negative and these patients are more difficult to diagnose. In such patients MSKUS can make a major difference in diagnosis with consequent effects of treatment and health.
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