Risks of mortality associated with common laboratory tests: a novel, simple and meaningful way to set decision limits from data available in the Electronic Medical Record

Alan B. Solinger; Steven I. Rothman

doi:10.1515/cclm-2013-0167

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Risks of mortality associated with common laboratory tests: a novel, simple and meaningful way to set decision limits from data available in the Electronic Medical Record

Alan B. Solinger und Steven I. Rothman

Veröffentlicht/Copyright: 14. Mai 2013

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Aus der Zeitschrift Clinical Chemistry and Laboratory Medicine Band 51 Heft 9

Abstract

Background: Laboratory tests provide objective measurements of physiologic functions, but are usually evaluated by demographic reference-intervals (RI), instead of risk-based decision-limits (DL). We show that hospital electronic medical record (EMR) data can be utilized to associate all-cause mortality risks with analyte test values, thereby providing more information than RIs and defining new DLs.

Methods: Our cohort was 39,964 patients admitted for any reason and discharged alive, during two 1-year periods, at Sarasota Memorial Hospital, Florida, USA. We studied five routinely-performed in-hospital laboratory tests: serum creatinine, blood urea nitrogen, serum sodium, serum potassium, and serum chloride. By associating a mortality odds ratio with small intervals of values for each analyte, we calculated relative risk of all-cause mortality as a function of test values.

Results: We found mortality risks below the population average within these proposed DLs: potassium 3.4–4.3 mmol/L; sodium 136–142 mmol/L; chloride 100–108 mmol/L; creatinine 0.6–1.1 mg/dL; blood urea nitrogen (BUN) 5–20 mg/dL. The DLs correspond roughly to the usually-quoted RIs, with a notable narrowing for electrolytes. Potassium and sodium have reduced upper limits, avoiding a “high-normal” area where the odds ratio rises 2 to 3 times the population average.

Conclusions: Any clinical laboratory test can be transformed into a mortality odds ratio function, associating mortality risk with each value of the analyte. This provides a DL determined by mortality risk, instead of RI assumptions about distribution in a “healthy” population. The odds ratio function also provides important risk information for analyte values outside the interval.

Keywords: blood chemical analysis/standards; blood urea nitrogen (BUN); chloride; clinical chemistry tests; creatinine; decision limits; potassium; reference standards; reference values; sodium

Corresponding author: Steven I. Rothman, 5019 Kestral Park Drive, Sarasota, FL 34231, USA, Phone: +1 866 794 0837, Fax: +1 866 255 0783

This work is based on and inspired by seminal research performed by Michael J. Rothman, PhD and one of the authors (SIR). G. Duncan Finlay, MD was instrumental in helping understand the issues around serum potassium, and medical issues in general. Alex Kiss, PhD is thanked for his calculation of the intra-class correlation coefficient and general advice. The authors acknowledge the contributions of two anonymous reviewers whose comments materially improved the manuscript. The non-profit F.A.R. Institute of Sarasota thanks PeraHealth, Inc. of Charlotte for their generous support of the authors’ research during this project.

Conflict of interest statement

Authors’ conflict of interest disclosure: The authors stated that there are no conflicts of interest regarding the publication of this article.

Research funding: None declared.

Employment or leadership: None declared.

Honorarium: None declared.

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Received: 2013-3-4

Accepted: 2013-4-4

Published Online: 2013-05-14

Published in Print: 2013-09-01

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https://doi.org/10.1515/cclm-2013-0167

Schlagwörter für diesen Artikel

blood chemical analysis/standards; blood urea nitrogen (BUN); chloride; clinical chemistry tests; creatinine; decision limits; potassium; reference standards; reference values; sodium