[The value of laboratory tests (author's transl)]

The diagnostic significance of various laboratory tests was studied at a Medical University Clinic and a regional hospital. Requests for such tests were graded on admission according to the criteria: (a) necessary for differential diagnostic decision; (b) part of routine admission programme. Results were assessed according to the criteria: (a) clinical "proof"; (b) of value in differential diagnosis; (c) pointing to another diagnosis; (d) unhelpful. Analysis of the results provided an interesting agreement: all doctors graded seven to ten tests as necessary. Those with the highest information content were the classical tests--erythrocyte sedimentation rate, serum-electrophoresis and blood sugar levels. 45.6% of those graded as necessary proved informative; 7.2% of routinely ordered tests provided pointers to another diagnosis. This percentage is the contribution of laboratory tests beyond what doctors consider as necessary for diagnosis. This additional value of laboratory tests is relatively high so that a reasonably extensive programme of laboratory tests on admission appears justified, especially if one adds the time factor to cost-effectiveness.