DO OUT-OF-OFFICE LABORATORY TESTS AFFECT DIAGNOSES IN GENERAL-PRACTICE

Objective - To find out whether the GP diagnosis changed by out-of-off ice laboratory test results and whether his diagnosis became more cert ain. Design - Descriptive study. Setting - Dutch survey of morbidity a nd interventions in general practice: stratified random sample of 161 GPs with a total list of 335 000 patients. Subjects - 2081 episodes of illness with at least one consultation with clinical chemistry, haema tology, or serology tests and at least one follow-up consultation. Mai n outcome measurements - Change in ICPC component or chapter between t he consultation in which a laboratory test was ordered and the follow up contact; change in exact ICPC code in cases with important diseases (infectious diseases, haematological disorders, endocrine abnormaliti es, auto-immune processes and malignancies (n=330)); change in certain ty of a diagnosis and change in somatic/psychosocial orientation. Resu lts - After laboratory tests done in the first consultation the ICPC c omponent changed in 46% of the diagnoses. Of the diagnoses made in fir st consultations without laboratory tests 41% changed in the follow up consultation. The diagnosis after laboratory tests was the same as be fore in 51% of the consultations with important diseases. Certainty ab out a diagnosis increased significantly after laboratory tests (p < 0. 001). An abnormal laboratory result did not affect the clinical certai nty of the general practitioner or the percentage of altered diagnoses . Conclusion - The usefulness of tests should be assessed not only in terms of the number of diagnoses changed or of the percentage of abnor mal results, but also in terms of the changed certainty concerning a d iagnosis.