R. von Essen

Incidence of Inflammatory Rheumatic Diseases in Finland

The incidence of inflammatory joint diseases was estimated by using two patient series. Firstly, the total yearly incidence of all such diseases together was estimated in a population of 15 600 persons of 16 years of age or older. Secondly, this overall incidence was divided by the ratio of different diseases obtained from a larger series of patients. The incidence of all inflammatory joint diseases was 218/100 000/year, 182 in males and 250 in females. The incidence was highest in middle age and lowest in old age. The incidence of ill-defined arthritides was five times that of definite rheumatoid arthritis in the youngest age group but in the oldest their frequencies were equal. In the whole population, the proportion of ill-defined arthritides was 2/5, of definite RA 1/5, of HL-A B27 associated diseases 1/5, and of other diseases 1/5 of the total incidence of inflammatory joint diseases. Because the frequency of HL-A B27 in all patients surveyed was about 40%, only half of the patients with this antigen showed a clinical picture of ankylosing spondylitis, Reiters disease, or reactive arthritis.

Culture of Joint Specimens in Bacterial Arthritis: Impact of blood culture bottle utilization

The advantage of inoculating blood culture bottles (BCB) with a bulk volume of joint fluid was studied by analyzing results for 155 positive specimens cultured in parallel in BCB and on conventional solid media. The specimens came from both natural and artificial joints of 89 patients treated in 1975–1994. One third of the specimens from patients not on antibiotics and half of the specimens from patients on antibiotics were positive by BCB culture only. Some fastidious or slow-growing organisms were detected exclusively by this method. Additional contaminants were also picked up, but the inconvenience was relatively minor. Alternative procedures for detecting microbes in joint specimens are discussed.

Bacterial Infection Following Intra-articular Injection: A Brief Review

The literature on 443 cases of postinjection bacterial arthritis is reviewed. The utter rarity of the condition may have been overemphasized in the past. Haematogenous infection of the puncture track may be more important than the transfer of skin bacteria into the joint.

Prospect for an Additional Laboratory Criterion for Rheumatoid Arthritis

The aim of the study was to establish the benefit of an additional hypothetical laboratory criterion for rheumatoid arthritis (RA), comprising positivity for antikeratin antibody (AKA) and/or antiperinuclear factor (APF). The tests were applied to a series of 308 hospital patients with various recent-onset inflammatory joint diseases who were followed for 3 years. The performance of APF and AKA was compared with rheumatoid factor (RF). The most sensitive (.72) but the least specific (.86) test for RA was the latex test. The most specific (.96) but the least sensitive (.33) test was AKA. Waaler-Rose and APF were intermediate. AKA and/or APF positive patients had significantly more erosions than patients negative for these autoantibodies. Despite the impressive performance characteristics of APF and AKA, the actual classification impact achieved, as compared to using RF as the sole laboratory criterion, turned out to be moderate. This is because the criteria proved to be interrelated. Unlike RF, AKA and APF are not suited to the general laboratory, at least not in their present form. Moreover they so far lack the broad data base of RF.

Antibody to stratum corneum (antikeratin antibody) and antiperinuclear factor: markers for progressive rheumatoid arthritis

The purpose of this study was to examine the relationship between circulating antibodies to stratum corneum (AKA) and antiperinuclear factors (APF) on one hand, and the x-ray progression of joint damage in chronic poly/oligoarthritis on the other hand. The analysis involved 133 patients with either rheumatoid or nonspecific arthritis derived from a cohort of 442 patients with recent onset arthritis. The patients were followed up for eight years with regular clinical, laboratory, and radiological evaluations. Radiographic evidence of joint destruction was quantitated by a radiographic index based on the Larsen grading. AKA and APF were detected, either at entry or at follow-up, in 26 and 54 patients, respectively. Seventy-six of the 133 patients had developed erosions. All AKA-positive patients had a rheumatoid factor-positive erosive poly-arthritis. The presence of APF was also associated with a progressive arthritis although four APF-positive patients had a non-erosive disease. Neither AKA nor APF were able to distinguish a particularly severe form of progressive RA.

Adenosine Deaminase Activity in Joint Effusions

The activity of adenosine deaminase (ADA) was determined in serum and synovial fluid of 98 patients with joint effusions of various causes. Compared with osteoarthritis, there were significantly higher mean synovial fluid ADA activities in seropositive rheumatoid arthritis (p less than 0.01), chronic seronegative polyarthritis (p less than 0.001), juvenile chronic arthritis (p less than 0.001) and reactive arthritis (p less than 0.001). In inflammatory joint diseases higher mean ADA activities in synovial fluid than in serum were observed, indicating a local release of ADA by cells within the joints. ADA activity in synovial fluid correlated with general disease activity as measured by haemoglobin concentration and erythrocyte sedimentation rate, and may provide an additional measure of the degree of inflammation in joint diseases.

Antibodies against Oxidised Low-density Lipoprotein in Juvenile Chronic Arthritis

Enhanced lipid peroxidation, reported to take place in rheumatoid joints and suggested to play a significant role in joint inflammation, led us to study the occurrence of antibodies against oxidised low-density lipoprotein (Ox-LDL Ab) in patients with juvenile chronic arthritis. Enzyme-linked immunosorbent assay was used to detect Ox-LDL Ab and antiphospholipid antibodies (aPL Ab) in sera from 84 patients and 91 controls. Elevated levels of Ox-LDL Ab were found in 14 patients (17%) as opposed to 4 controls (4%; p < 0.01). Similarly, 14 patients had an elevated aPL Ab level and a fairly good correlation between Ox-LDL Ab and aPL Ab (r = 0.52) existed in the patients. The increased frequency of elevated levels of Ox-LDL Ab may reflect lipid peroxidation occurring in rheumatoid joints but crossreactivity with aPL Ab for the induction of Ox-LDL Ab cannot be excluded.

Immunonephelometric Quantitation of Complement Split Product (C3d) Plasma Levels in Rheumatic Disease

A simple method is described for routine quantitative determination of C3d by laser nephelometry after precipitation of intact C3 by polyethylene glycol. Plasmas from 292 patients with different types of rheumatic disease was tested. Elevated C3d levels were a far more common finding than low levels of complement components C3 or C4, but despite the increased sensitivity, the test only seemed diagnostically useful for systemic lupus erythematosus and MCTD. Though a better test than the quantitation of C3 and C4, the value of C3d determination in rheumatic disease seems to be limited.

Low-Dose Penicillamine Treatment of RA: Comparison of 600 mg and 300 mg Regimens

Results and side effects were compared in 100 patients with rheumatoid arthritis treated with 600 mg penicillamine daily and 100 patients given 300 mg daily. While haemoglobin rose and erythrocyte sedimentation rate dropped in both the 300 mg and the 600 mg cohort, no significant improvement in clinical measure could be demonstrated for the low-dose patients. Medication was discontinued because of side effects in 30 patients on the low dose and 41 patients on the higher dose. Only 8 renal complications were seen among the low-dose patients, vs. 26 in the 600 mg cohort. However, 6 patients on the low dose vs. none on the higher dose dropped out because of inadequate therapeutic effect. Further downward adjustment of currently used daily dose, though desirable because of the relationship between dosage and side effects, seems doomed by unacceptable loss of therapeutic efficacy in most cases.

Quality Control of Rheumatoid Factor (RF) Testing in Finland

RF has been on the national laboratory quality control program since 1981. A pilot study had showed that most participants would be small laboratories performing qualitative slide latex tests only. Since we nevertheless wanted to be able to extrapolate test sensitivity data for each laboratory, we have sent out sets of 5-6 coded samples that in fact constitute a double dilution titration series. RF positive sera were pooled and the material calibrated with the WHO RF standard. The samples have contained 5-160 IU RF/ml and have been distributed once a year. The number of participants has varied from 58 to 104. Interlaboratory variation has diminished considerably since 1981. Inversions in the estimates of RF contents in the sample series have been notably rare. Waaler-Rose returns have mostly been too small to permit statistical evaluation. The same so far goes for the turbido- and nephelometric methods, in use since 1985.