Erroneous laboratory results can adversely affect medical decisions. While the prevalence of laboratory errors has been well documented,1 their consequences, particularly when they go unnoticed, are less well reported. We describe the clinical consequences of a series of falsely elevated laboratory results that went unnoticed for 10 days.

On 20 June 2012, an endocrinologist alerted the laboratory to possible spurious results after noticing extremely high insulin-like growth factor-1 (IGF-1) concentrations in two clinically asymptomatic patients. The ensuing investigations revealed an error in the analyser (Immulite 2000, Siemens, Surrey, UK) that performed five endocrine tests, including IGF-1, and affected all results reported on 11 June. The error eluded the internal quality control (QC) testing performed routinely prior to patient sample analysis.

All erroneous results (n=63) were unknowingly reported. Retesting of all specimens belonging to 49 patients revealed 2.1- to >108-fold reductions in their results (see online supplementary table S1). The ranges of the erroneous results and the correct values (in parentheses), respectively, were: adrenocorticotrophic hormone (ACTH, n=10), 15.3–132 pmol/l (<1.11–36.6); anti-thyroglobulin antibodies, 67– >3000 IU/ml (n=15, <20–830); anti-thyroid peroxidase antibodies, 37– >1000 IU/ml (n=7, <10–876); growth hormone, 2.12–188 µg/l (n=10, 0.35–9.63); IGF-1 603–2263 ng/ml (n=21, 54–292). All ordering physicians were immediately notified of the amended results. The engineers of the manufacturer were immediately brought in to conduct an extensive investigation, which included checking for reagent/probe/tubing contamination, reagent …