The impact of calcium assay change on a local adjusted calcium equation.

Ann Clin Biochem

Department of Clinical Biochemistry & Metabolic Medicine, Liverpool Clinical Laboratories, Royal Liverpool & Broadgreen University Hospitals NHS Trust, Liverpool, UK.

Published: March 2016

AI Article Synopsis

  • The study evaluated the effects of changing the calcium testing method from cresolphthalein complexone to NM-BAPTA on local adjusted calcium equations.
  • 13,482 results were analyzed to derive a new adjusted calcium equation using the updated method, which showed only minor changes that were not clinically significant.
  • The findings emphasized the need to regularly re-evaluate local adjusted calcium equations and acknowledged that local reference intervals might differ from national consensus guidelines.

Article Abstract

Background: Deriving and validating local adjusted calcium equations is important for ensuring appropriate calcium status classification. We investigated the impact on our local adjusted calcium equation of a change in calcium method by the manufacturer from cresolphthalein complexone to NM-BAPTA.

Methods: Calcium and albumin results from general practice requests were extracted from the Laboratory Information Management system for a three-month period. Results for which there was evidence of disturbance in calcium homeostasis were excluded leaving 13,482 sets of results for analysis. The adjusted calcium equation was derived following least squares regression analysis of total calcium on albumin and normalized to the mean calcium concentration of the data-set. The revised equation (NM-BAPTA calcium method) was compared with the previous equation (cresolphthalein complexone calcium method).

Results: The switch in calcium assay resulted in a small change in the adjusted calcium equation but was not considered to be clinically significant. The calcium reference interval differed from that proposed by Pathology Harmony in the UK.

Conclusions: Local adjusted calcium equations should be re-assessed following changes in the calcium method. A locally derived reference interval may differ from the consensus harmonized reference interval.

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Source
http://dx.doi.org/10.1177/0004563215583699DOI Listing

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