RESEARCH - Is rheumatoid factor (RF) still a superior test for the diagnosis of RA?

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Rheumatol Int. 2010 Jun;30(8):1115-9. Epub 2010 Jan 8.

Is rheumatoid factor still a superior test for the diagnosis of

rheumatoid arthritis?

Singh U, Vishwanath A, Verma PK, Singh NK, Shukla RC, Singh S, Singh

S, Sonkar GK.

Department of Pathology, Institute of Medical Sciences, Banaras Hindu

University, Varanasi, Uttar Pradesh, 221005, India.

Abstract

The diagnosis of rheumatoid arthritis (RA) is based primarily on the

1987 revised American College of Rheumatology criteria for RA, which

considers mainly the clinical symptoms. But typical clinical symptoms

of RA are not manifested completely in early disease course.

On the other hand, appreciable advantages have been made in the

therapeutic strategy of RA in the last decade and highly effective

disease-modifying anti-rheumatic drugs are available now for the

control of RA. The treatment strategy for the control of early RA is

aggressive. Thus, a highly specific and early diagnostic marker is

needed for the detection of RA.

Our study is an attempt to see the role of anti-CCP2 antibody (claimed

to be highly specific and early diagnostic tool) in the diagnosis of

RA. We studied 119 cases of RA in terms of clinical symptoms, disease

duration and various autoantibody [including rheumatoid factor (RF),

anti-CCP2 antibody, antinuclear antibody, anti-dsDNA] and C-reactive

protein status. All the tests were also performed in 26 age and

sex-matched healthy controls.

Estimation of antibodies was done by quantitative ELISA. IgM RF was

positive in 47.89% cases (p value = 0.000), followed by IgG RF

(42.01%, p = 0.000) and IgA RF (36.97%, p = 0.000). RF was positive in

64.7% RA cases (p value = 0.000) when all three isotypes were tested

together. RF was also detected in one healthy control. In 92 cases,

anti-CCP2 Ab was done, hence other data were analyzed further in 92

cases only. Anti-CCP2 Ab was positive (cut-off = 15.0 U/ml) in only

50% RA patients but none of the healthy controls was positive for it.

Swelling of joints was seen in 82.6% anti-CCP2 Ab positive cases (p

value = 0.092) when compared with anti-CCP2 Ab negative cases (67.4%)

while among RF positive cases, only 65.4% ((p value = 0.010) cases had

swelling of joints. Out of 39 RA cases presenting with disease

duration less than 1 year, only 48.71% patients were anti-CCP2 Ab

positive while RF was positive in 61.53% patients.

Utility of various combined autoantibody tests revealed that if one

does all isotypes of RF (IgG, IgA and IgM) only, then 64.7% RA cases

can be diagnosed and if anti-CCP2 Ab is added to it, the sensitivity

increases to 75.56%. Thus, our study concludes that anti-CCP2 Ab is

not a sensitive test for the diagnosis of RA neither it is useful in

early diagnosis of RA, but it increases the sensitivity if added with

all RF isotypes.

PMID: 20058015

http://www.ncbi.nlm.nih.gov/pubmed/20058015

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