"Rheumatoid Arthritis" with Negative Serological Reaction
Authors: A. St. J. Dixon
Journal: Annals of the Rheumatic Diseases (1960)

This paper describes a follow-up study of in- patients with severe active rheumatoid polyarthritis, in whom the sensitized sheep cell agglutination test (S.C.A.T., Ball, 1950) was found to be negative. PatientsThe patients reviewed in this study comprise all those treated as in-patients in the rheumatism beds of the Manchester Royal Infirmary during the period 1948 to 1956 inclusive, who were sero-negative, but in whom, during their first admission, no diagnosis other than rheumatoid arthritis or polyarthritis of undetermined type could be made by the accepted criteria (Ropes, Bennett, Cobb, Jacox, and Jessar, 1956).An erythrocyte sedimentation rate of over 20 mm./hr (Westergren) was also required as a criterion of disease activity. 63patients conformed to this definition and these were selected for followup.This number represents some 6 per cent. of all the patients admitted to the rheumatism beds during these years.While the patients were in hospital the S.C.A.T. was done weekly; some tests were also done at subsequent out-patient atten- dances, but in all cases the test was repeated at the follow-up examination. Serological CriteriaFor this study it was desirable to eliminate borderline results in the test so that a negative test was defined as one in which no agglutination was observed after incubation for 18 hrs with serum dilutions greater than 1: 8.This criterion for a negative test is more strict than that described in previous publications from this Centre, in which agglutination with a titre of 1: 32 is accepted as a minimal positive result (Kellgren and Ball, 1959).Great care has been taken to maintain standard sensitivity of the test over the years, and all new batches of reagents are adjusted to give standard results with arbitrary standard sera.Control sera of known titre are tested with each batch of un- known sera, and the whole batch is retested or rejected if the controls are unsatisfactory.Control sera are stable for at least a year.Thus changes in the S.C.A.T. observed at follow-up may be regarded as real and not "technical".This study group of patients was tested frequently.So that the results of all available tests could be taken into account, those patients in whom not more than one borderline titre of 1: 16 was found amongst at least four negative tests within any 6 months' period were included as sero-negative and were not excluded from the follow-up series, but if more than 25 per cent. of the readings during any 6 months were 1 :16 or more, the case was excluded from follow-up.In the remainder of this paper, the convention of reciprocal titre will be observed.Thus a S.C.A.T. of less than 4, 4, or 8 is negative, of 32, 64, etc., positive, and of 16 "doubtful positive".Diagnostic Criteria and Predictability of the S.C.A.T.In typical, sero-positive nodular rheumatoid arthritis, the disease may start in many ways, and the pattern of joint involvement at onset may differ from that seen later.Nevertheless, it has been shown that in hospital in-patients with polyarthritis the results of the S.C.A.T. can be predicted from the clinical and radiological features of the case with considerable accuracy (Kellgren and Ball, 1959) and as a result of this the clinical features of fullydeveloped sero-positive rheumatoid arthritis have become more clearly defined.Typical rheumatoid arthritis showed symmetrical peripheral polyarthritis, including (as a minimum) involvement of both wrists, the second and third metacarpophalangeal joints of both hands, and the lateral meta- tarsophalangeal joints in the feet.In the more 209 copyright.