Selected laboratory in pediatric emergency care.

The superiority of either a complete blood count, erythrocyte sedimentation rate, or C-reactive protein as a generic, global screening test for bacterial infection in infants or children has not been clearly demonstrated. The few claims of superiority for one determination over another relate more to the clinical setting than marginal differences in sensitivity or specificity. Neither the complete blood count, erythrocyte sedimentation rate, or C-reactive protein has proved sensitive enough of predicting invasive bacterial infection that it can be used as an isolated measure upon which major management decisions can safely be based. Several investigators have therefore addressed whether these tests can complement each other. Unfortunately, acquisition of multiple nonspecific laboratory tests in a given clinical situation may yield widely divergent results. The C-reactive protein, complete blood count, erythrocyte sedimentation rate, and zeta sedimentation ratio are all comparably priced in the $15.00 to $30.00 range. However, if multiple tests are obtained, the cost of this approach may become unacceptably high. Current practice advocates a careful evaluation of an ill pediatric patient in an Emergency setting. The initial clinical impression of an experienced clinician based on history and physical examination frequently provides dependable information with which to direct subsequent evaluation. If bacterial infection ranks high on the differential list, relevant laboratory studies should be considered. Observation of quantitative and qualitative changes of the hematologic profile or rate of erythrocyte sedimentation are adequate tools in specific circumstances. With the resurgence of interest in the use of C-reactive protein, it too may join the ranks of convention in selected settings.