Serum complement levels in rheumatoid arthritis. A longitudinal study of 43 cases with correlation of clinical and serological data including rheumatoid factor and thermolabile inhibitor of the F-II L.P. test.
Authors: A F Schubart, R W Ewald, W C Schroeder, H J Rothschild, D N Bhatavadekar, P K Pullen
Journal: Annals of the Rheumatic Diseases (1965)

Studies of serum complement levels of patients with rheumatoid arthritis have produced conflicting results (Table I, overleaf).Early investigators, using a 100 per cent.end-point method for the determination of haemolytic activity, reported normal or reduced values (Cadham, 1926; Schnabel, 1933; Rachmilewitz and Silberstein, 1937).With the more refined and dependable technique of the 50 per cent.haemolysis determination of serum complement, raised values were found by Vaughan, Bayles, and Favour (1951), Wedgwood and Janeway (1953), Williams and Law (1958), and Ellis and Felix-Davies (1959).Kellett (1954) concluded that "Isolated readings in the majority of cases of rheu- matoid arthritis would lead to results well within the normal range".Similar results were obtained by Laurell and Grubb (1958), Asherson (1960), and Jonsen and Kass (1961).Recently Perlick (1962) and Geidel, Selle, and Schabinski (1964) recorded predominantly reduced complement levels.In part, some of these discrepancies may be explained by the use of different techniques of complement assay.The main reason, however, must lie in the small number of cases studied pre- dominantly with a single complement determination.Such cross-sectional studies using a limited sample could produce erratic results ifsignificant fluctuations of serum complement levels occurred during the course of rheumatoid arthritis.In order to determine whether or not such changes of serum complement levels take place during the course of rheumatoid arthritis, a longitudinal clinical and serological study was conducted at University Hospital and Montebello State Hospital, Baltimore, Maryland.Data were obtained which explain the discrepancy of previous publications, and the results are presented below.Material 43 patients with classical or definite rheumatoid arth- ritis (Ropes, Bennett, Cobb, Jacox, and Jessar, 1959) were selected at random for examination at 4-to 8-week intervals in the Arthritis Clinic of University Hospital and on the wards of the Montebello State Hospital, Baltimore, Maryland.The clinical evaluation and the assessment of disease activity were performed according to a protocol which has already been published in detail (Schubart, Cohen, and Calkins, 1964).Results of every examination were recorded separately for each patient.Disease activity was classified as active or inactive (remission).Active disease was graded as minimal, moderate, or severe.The patients were divided into groups according to the treatment received during the course of observation; 26 patients (Cases 1-26) were treated with salicylates only, and twelve (Cases 29-40) received steroids at some time or another.Steroid treatment consisted of a minimum dose schedule required for partial suppression of disease activity and did not exceed 20 mg.Prednisone per day in any one of the patients.Three patients (Cases 41-43) received gold treatment during the time of observation. MethodsSerum was obtained at each re-examination.In order to preserve unstable serum constituents, techniques published previously were employed (Schubart, Rothschild, Schroeder, Ewald, and Tuerk, 1963).Sera were stored at -70°C.The following tests were carried out on every serum:(1) Serum complement levels were determined and expressed in C'-H50 haemolytic units following the technique of Mayer (1961).For details see Schubart and others (1963).