DISTRIBUTION OF CASES OF SYSTEMIC LUPUS-ERYTHEMATOSUS AT TIME OF FIRST SYMPTOM IN AN URBAN AREA

Objectives-To determine the geographical distribution of cases of syst emic lupus erythematosus (SLE) in a defined geographical area in the E ast Midlands, UK, and, in particular, to search for spatial variation in cases that may implicate the role of environmental factors in SLE a etiology. Methods-Six methods of case ascertainment were used. The pos tcode of the patient's domicile at time of first definite symptom of S LE was used for analysis which included case mapping, probability mapp ing by electoral ward, and variogram analysis. Results-The study area population of 613 700 contained 200 SLE patients, 188 of whom experien ced their first symptom whilst residing in the area. Case mapping reve aled 12 SLE patients residing within an area of one square mile, inclu ding four men and six patients with RNP antibodies. The use of probabi lity mapping showed five wards in close proximity to each other to hav e a greater number of SLE cases than would be expected by chance (p < 0.1). The 'cluster' of patients seen on the case map fell into two war ds which showed a significant excess of cases only when combined (p = 0.006). The variogram of the incidence rates for each ward did not con firm any structure or pattern to the distribution of cases for the who le area. Conclusions-Some areas have a greater than expected prevalenc e of SLE. The normal result from variogram analysis suggests that the cause(s) for these excess number of cases does not have an effect acro ss the whole study area.