Tighter precision target required for lactate testing in patients with lactic acidosis

Kristen A. Versluys; Sharon Redel; Andrea N. Kunst; Mark Rimkus; Dat Chin; David Tran; Daniel Holmes; George S. Cembrowski

doi:10.1515/cclm-2013-0685

Article

Tighter precision target required for lactate testing in patients with lactic acidosis

Kristen A. Versluys , Sharon Redel , Andrea N. Kunst , Mark Rimkus , Dat Chin , David Tran , Daniel Holmes and George S. Cembrowski

Published/Copyright: January 8, 2014

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From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 52 Issue 6

Abstract

Background: Allowable analytic errors are generally based on biologic variation in normal, healthy subjects. Some analytes like blood lactate have low concentrations in healthy individuals and resultant allowable variation is large when expressed as a coefficient of variation (CV). In Ricós’ compendium of biologic variation, the relative pooled intra-individual lactate variation (s_i) averages 27% and the desirable imprecision becomes 13.5%. We derived biologic variability (s_b) from consecutive patient data and demonstrate that s_b of lactate is significantly lower.

Methods: A data repository provided lactate results measured over 18 months in the General Systems intensive care unit (ICU) at the University of Alberta Hospital in Edmonton, Canada. In total 54,000 lactate measurements were made on two point-of-care Radiometer 800 blood gas systems operated by Respiratory Therapy. The standard deviations of duplicates (SDD) were tabulated for the intra-patient lactates that were separated by 0–1, 1–2…up to 16 h. The graphs of SDD vs. time interval were approximately linear; the y-intercept provided by the linear regression represents the sum of s_b and short-term analytic variation (sa):y0=(sa2+s)b212. The short-term s_a was determined from imprecisions provided by Radiometer and confirmed with onsite controls. The derivation of s_b was performed for multiple patient ranges of lactate.

Results: The relative desirable lactate imprecision for patients with lactic acidosis is about half that of normal individuals.

Conclusions: As such, evaluations of lactate measurements must use tighter allowable error limits.

Keywords: allowable error; biologic variation; intensive care unit; lactate

Corresponding author: Kristen A. Versluys, Department of Laboratory Medicine, University of Alberta Hospital, 4B1.24 Walter C. Mackenzie Center, 8440 112 Street, Edmonton, AB T6G 2B7, Canada, E-mail: kversluy@ualberta.ca

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Presented at National Meeting of the American Association for Clinical Chemistry in Houston, TX on August 2013.

Received: 2013-8-23

Accepted: 2013-11-25

Published Online: 2014-1-8

Published in Print: 2014-6-1

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Articles in the same Issue

https://doi.org/10.1515/cclm-2013-0685

Keywords for this article

allowable error; biologic variation; intensive care unit; lactate