Prevalence and influence of diagnostic tests for acute respiratory tract infections in primary care.

Abstract

General practitioners (GPs) use diagnostic tests to help distinguish between viral and bacterial acute respiratory tract infections (ARTI). We investigated the prevalence of these tests, and how tests are associated with diagnosis, treatment and patient satisfaction. As part of a clinical trial, 45 GPs screened 1108 patients with ARTI and collected information on signs and symptoms, diagnostic test results, and subsequent diagnosis and treatment. A sample of 636 patients was interviewed after 7 days and their opinions recorded. We used multivariate mixed models to estimate associations between the use of tests and (1) baseline characteristics, (2) subsequent antibiotic treatment, and (3) patient satisfaction. GPs carried out at least one test in 42% of the 1108 patients screened. The tests used were (percentage of patients): CRP (35%), leucocyte count (17%), rapid Strep A (9%), chest X-ray (5%), sinus X-ray (1%), and throat culture (1%). The use of tests was associated with increasing patient age, education, and degree of discomfort. Antibiotic therapy was strongly associated with a positive test, with odds ratios of 26 (95% CI, 10-67) for a CRP above 50 mg/l; 9.6 (95% CI, 3.6-26) for a leucocyte count above 10,000/microl; and 122 (4.4-3435) for a positive StrepA test. There was no evidence of an association between the use of tests and patient satisfaction. Nearly half of these patients with ARTI received a diagnostic test. Older patients, those with higher education and those in more discomfort were more likely to get tests. A positive test was strongly associated with antibiotic treatment.