A clinical and serological comparison of group A versus non-group A streptococcal reactive arthritis and throat culture negative cases of post-streptococcal reactive arthritis

Objective-To identify clinical and serological differences of patients with reactive arthritis after infection with Lancefield group A beta-haemolytic streptococci (GAS), compared with non-group A-that is, group C or G strept ococci (NGAS:GCS/GGS), and a group of culture negative or unidentified stre ptococci (GUS). Methods-A prospective study of consecutive patients with reactive arthritis after serologically or culture confirmed infection with beta-haemolytic st reptococci, presenting to the outpatient department of rheumatology from Ja nuary 1992 until January 1998. Alternative causes for reactive arthritis we re excluded. Main outcome measures were clinical and serological characteri stics including antistreptolysine-O (ASO) and antideoxyribonuclease-B (anti DNase-B) antibody titres. Results-41 patients (female/male ratio 22/19; mean (SD) age 38 (13) years) with reactive arthritis were included. Culture of throat swab was positive in 13 cases (32%): 6 (15%) GAS, 7 NGAS (17%), that is, 5 (12%) GCS, 2 (5%) GGS. In 28 cases throat culture remained negative resulting in a group of u nidentified streptococci; antibiotic pre-treatment had been given by the ge neral practitioner in 18 cases (64%). Arthritis was non-migratory, the numb er of arthritic joints in GAS and NGAS was similar, whereas in NGAS patient s fewer joints were involved than in GUS: mean (SEM) 36 swollen joint index : 3.3 (1.0) in NGAS v 5.6 (1.0) in GUS (p < 0.005); 28 swollen joint index: 2.9 (1.0) in NGAS v 4.3 (0.8) in GUS (p < 0.05). Extra-articular manifesta tions-that is, erythema nodosum/multiforme, AV conduction block or hepatiti s-were observed after GAS or GUS infection, but not after NGAS infection. A SO and/or antiDNase-B rose significantly in all patients. The maximal titre s for ASO and antiDNase-B in 41 PSRA patients were: mean (SEM) 1242 (232) U /1 and 890 (100) U/1 respectively; the maximal ASO titres were similar in t he three groups: mean (SEM) 1125 (185) in GAS, 625 (160) in NGAS (GAS v NGA S: p = 0.17), and 1430 (320) U/1 in GUS (NGAS v GUS: p = 0.10). AntiDNase-B titres were: mean (SEM) 1075 (180) in GAS, 375 (105) in NGAS (GAS v NGAS: p < 0.01), and 995 (125) U/1 in GUS (NGAS v GUS: p < 0.005). ASO: antiDNase -B ratios were: mean (SEM) 0.89 (0.21) in GAS, 2.60 (0.76) in NGAS (GAS v N GAS: p < 0.05), and 1.43 (0.28) in GUS (NGAS v GUS: p = 0.12). Conclusion-Post-streptococcal reactive arthritis occurs not infrequently. D ifferentiation of PSRA based on the causative streptococcal strain is frequ ently thwarted by negative throat cultures. Sometimes extra-articular manif estations are present that exclude NGAS as the causative organism. Serologi cally, lower antiDNase-B titres may be indicative for primary NGAS infectio n; the ASO/antiDNase-B ratio may be of additive value for differentiation i n cases of a negative throat culture: the higher ASO/antiDNase-B ratios sug gesting primary NGAS infection. In reactive arthritis, serological monitori ng consisting of a simultaneous titration of antiDNase-B and ASO, seems to be of clinical importance to trace GAS induced cases, especially when throa t cultures remain negative.