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The mean abnormal result rates of laboratory tests ordered in the emergency department: shooting percentage insights from a multi-centre study

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While there is concern about excessive laboratory test ordering in the ED, it is difficult to quantify the problem. One solution involves the Mean Abnormal Result Rate (MARR), which is the proportion of tests ordered that return abnormal results. The primary objective of this study was to calculate MARR scores, and factors associated with MARR scores, for tests ordered between April 2014 and March 2019 at adult EDs in Calgary.


Administrative data were obtained for 40 laboratory tests that met selection criteria. One possible MARR correlate, physician experience, was quantified for 209 ED physicians as number of years since licensure. Analyses were descriptive where appropriate for whole-population data.


The condensed dataset comprised 3,395,312 test results on 415,653 unique patients. The aggregate 5-year MARR score was 40.1%. The highest per-test score was for BNP (80.5%), while the lowest was for glucose (7.9%). MARR scores were higher for nurse-initiated orders than for physician-initiated orders (44.7% vs. 38.1%). The MARR score correlated inversely with number of tests per order (r = − 0.90; 95% confidence interval [CI] − 0.65 to − 0.94; p < 0.001) and directly with physician experience (r = 0.28, 95% CI 0.20 to 0.27; p < 0.001).


This is the first study to measure MARR scores in an ED setting. While lower scores (close to 5%) are less optimal in principle, ideal scores will depend on the clinical context in which tests are used. However, once departmental benchmarks are established, MARR score-monitoring allows efficient tracking of ordering practices across millions of tests.



Bien que l'on s'inquiète d'une commande excessive de tests de laboratoire dans le service d'urgence, il est difficile de quantifier le problème. Une solution implique le taux de résultat anormal moyen (MARR), qui est la proportion de tests commandés qui renvoient des résultats anormaux. L'objectif principal de cette étude était de calculer les scores MARR, et les facteurs associés aux scores MARR, pour les tests commandés entre avril 2014 et mars 2019 dans les services d'urgence pour adultes à Calgary.

Les méthodes

Des données administratives ont été obtenues pour 40 tests de laboratoire répondant aux critères de sélection. Une corrélation possible du MARR, soit l’expérience des médecins, a été quantifié pour 209 médecins urgentistes en nombre d'années depuis l'autorisation d'exercer. Les analyses étaient descriptives, le cas échéant, pour les données sur l’ensemble de la population.


L'ensemble de données condensé comprenait 3,395,312 résultats de tests sur 415 653 patients uniques. Le score MARR global à 5 ans était de 40,1%. Le score le plus élevé par test était pour le peptide cérébral natriurétique BNP (80,5%), tandis que le plus bas était pour le glucose (7,9%). Les scores de MARR sont plus élevés pour les ordonnances initiées par les infirmières que pour les ordonnances initiées par les médecins (44,7% contre 38,1%). Le score MARR s’est corrélé inversement avec le nombre de tests par ordre (r = − 0,90; intervalle de confiance de 95 % [IC] − 0.65 to − 0,94; p < 0.001) et directement avec l’expérience du médecin (r = 0.28, IC à 95 % 0.20–0.27; p < 0.001).


Il s’agit de la première étude à mesurer les scores du MARR dans un contexte de service d’urgence. Bien que des scores inférieurs (près de 5%) sont moins optimaux en principe, les scores idéaux dépendront du contexte clinique dans lequel les tests sont utilisés. Cependant, une fois les points de repère ministériels établis, la surveillance des scores du MARR permet de suivre efficacement les pratiques de commande sur des millions de tests.

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We thank Shawn Dowling, MD for a critical review of this manuscript, and Zane Ramdas and Patricia Johnson for assistance with data collection.


This research received no specific grant from any funding agency, commercial or not-for-profit sectors.

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Correspondence to Eddy Lang.

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Enwere, E.K., Wang, D., Guo, M. et al. The mean abnormal result rates of laboratory tests ordered in the emergency department: shooting percentage insights from a multi-centre study. Can J Emerg Med 24, 35–38 (2022).

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