High risk results: the evidence for total serum calcium alert thresholds

‘High risk results’ (HRR) are defined as those results requiring immediate medical attention and action due to the high risk of imminent death or major patient harm. International surveys have found significant inter-laboratory variation in the methods and evidence used to determine HRR alert thresholds, posing risk to patient safety. In response, the Australasian Association of Clinical Biochemists (AACB) Working Party is compiling an evidenced based list of alert thresholds as a reference for Australasian laboratories, to assist the harmonisation of HRR reporting. This list will include thresholds for calcium, as both hyper- and hypocalcaemia carry the risk of developing into life threatening conditions such as tetany and cardiac arrhythmia.

A systematic review was performed to appraise any existing evidence for critical calcium alert thresholds. The search was conducted using Medline, Embase and Scopus from 1975 through October 2018. A total of 48 papers were identified for full-text review, each assessed for quality of evidence with studies based on patient outcome ranked highest. We report on the findings of this review and comment on the relationship between current thresholds and patient clinical outcome. It is intended that these findings will inform the AACB Working Party in determining appropriate alert thresholds.