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Verstappen WHJM, ter Riet G, Dubois WI, Winkens R, Grol RPTM and van der Weijden T. Variation in test ordering behaviour of GPs: professional or context-related factors? Family Practice 2004; 21: 387‐395. Objective. The aim of this study was to describe GPs’ test ordering behaviour, and to establish professional and context-related determinants of GPs’ inclination to order tests. Methods. A cross-sectional analysis was carried out of 229 GPs in 40 local GP groups from five regions in The Netherlands of the combined number of 19 laboratory and eight imaging tests ordered by GPs, collected from five regional diagnostic centres. In a multivariable multilevel regression analysis, these data were linked with survey data on professional characteristics such as knowledge about and attitude towards test ordering, and with data on context-related factors such as practice type or experience with feedback on test ordering data. The main outcome measure was the percentage point differences associated with professional and context-related factors. Results. The total median number of tests per GP per year was 998 (interquartile range 663‐1500), with significant differences between the regions. The response to the survey was 97%. At the professional level, ‘individual involvement in developing guidelines’ (yes versus no), and at the context-related level ‘group practice’ (versus single-handed and two-person practices) and ‘more than 1 year of experience working with a problem-oriented laboratory order form’ (yes versus no) were associated with 27, 18 and 41% lower numbers of tests ordered, respectively. Conclusion. In addition to professional determinants, context-related factors appeared to be strongly associated with the numbers of tests ordered. Further studies on GPs’ test ordering behaviour should include local and regional factors.

For urinary tract infections (UTI), diagnostic testing appears to be reliable and simple to perform. This particularly seems to hold true for test strips. In studies the validity of several urine tests proved to be high. These studies were, however, performed under optimal and standardized conditions. Their results therefore do not reflect daily practice. In this study the validity of urine tests for UTI is deterined under daily practice conditions, without the use of a protocol. The results show a validity considerably lower than under optimal conditions. Specificity in particular was lower, even for simple tests like the nitrite reaction. Under daily practice conditions, UTI can neither be confirmed nor excluded sufficiently on the outcome of a urinary sediment or test strip.

So far, the validity of urine dipslides has been studied only under optimal conditions, which may not reflect the situation in daily practice.We studied the validity of the urine dipslide as performed under daily practice conditions and assessed the influence of the incubation period (24 h versus 48 h) on validity.Fresh urine samples of patients with signs/symptoms of a possible urinary tract infection (UTI) were examined in general practice via a nitrite test, a urine sediment and a dipslide. A second dipslide was inoculated and sent to the hospital microbiology laboratory for culture. This culture acted as gold standard. We calculated the sensitivity and specificity of the tests performed.Of the 273 patient episodes included, 62% had a UTI (166 of 268 cultures). The sensitivity of the dipslide performed in daily general practice was 73% and the specificity was 94%.The validity of the dipslide read under practice conditions is lower than under optimal conditions. Actions to improve performance are needed. Nonetheless, using the dipslide instead of the sediment as a second step after the nitrite test would improve the diagnostic work-up of UTI.

The number of good quality studies on the effect of feedback and reminders on diagnostic and preventive activities in ambulant practice is still low. The interventions and procedures studied differ widely, and the reporting of the results is insufficiently precise. This makes comparison difficult and quantitative pooling impossible. Nevertheless, the literature supports the contention that feedback reduces the use of diagnostic tests and the costs thereby engendered. It also discloses a positive effect of feedback on the adherence of medical practice to guidelines or standards. In this respect, the effect of reminders seems to exceed that of classical methods of feedback. There is still a need for research on the effect of feedback, reminders and other instruments for quality assurance on various aspects of medical performance in different settings.