Relevance of the emergency department’s diagnostic tests according to the guidelines and impact on the emergency length of stay

Background: Clinical examination may need to be completed by biological tests. In the Emergency Department (ED), a simplified access to laboratory tests results in an uncorrelated prescription with guidelines. The aim of our study was to assess the relevance of laboratory tests according to the clinical situation. The secondary objective was to assess their impact on the ED length of time. Material and methods: Observational, retrospective, singlecenter study, based on the analysis of computer records, of over 18 years old external patients for one of the following diagnoses: asthma exacerbation, renal colic, acute cystitis, pyelonephritis, suicide attempts by self-poisoning with benzodiazepines, drunkenness, pneumonia (Fine 1), reflex syncope, minor head injury, first convulsive seizure, over a 4-month period. Results: A total of 409 patients were enrolled. Among them, 43% of patients had laboratory test prescriptions adapted to their clinical situation (from 0% in case of renal colic to 89% in case of mild head trauma). Practitioners with more than 5 years of experience respected guidelines less than others (p = 0.02). The complete blood count, plasma electrolytes, and C-reactive protein level determinations were the most frequently prescribed tests. The ED length of stay was significantly shorter if prescription was appropriate to clinical situation (30 [6–130] vs. 170 [68–245] minutes; p < 0.001). Conclusion: A large number of laboratory tests were not recommended for the management of clinical situations encountered. The main impact was an increased ED length of stay.