[Population-based study of the epidemiology of diagnostic test ordering]

To identify type of service, frequency, and individual patient determinants associated with diagnostic test ordering in medical appointments.

A population-based study included 3,100 adults aged 20 years or older, living in the city of Pelotas, Southern Brazil. Sampling was carried out in multiple stages. Information were collected by means of a questionnaire, administered between October and December 2003. Multivariate analyses were carried out using Poisson Regression, based on a conceptual model. A sub-study was also conducted based on the test requests received during one workday in all laboratories in the city processing requests from both the public and private sectors.

Fifty-five percent of subjects reported having had medical appointments during the three-month period investigated. Of these, 60% reported more than one appointment, generating a total 4,167 appointments, most of which were paid for by health plans (38%). Diagnostic test were requested in 55% of appointments. Women and diabetic patients were more likely to have tests ordered. The greater the age (p<0.001) the higher the socioeconomic level (p=0.04), and the number of medical appointments (p<0.001), the greater the proportion of appointments leading to test requests. Mean waiting time between test request and sample collection was six days for the private sector and 21 days for the public sector (p<0.001). The mean number of tests per request was 4.4.

The proportion of appointments leading to the request for some type of diagnostic test was in accordance with Brazilian recommendations. The waiting time before sample collection indicates an excessive number of tests per request and/or insufficient financial resources to fulfill the demand for tests.