Mass Spectrometry-based Diagnostics: The Upcoming Revolution in Disease Detection Has Already Arrived

Abstract

Interference by hemoglobin is clearly labeled in the VITROS ® Troponin I assay’s “Instructions For Use” and Package Insert. The hemoglobin con-centrations used and the differences measured are stated under“Limita-tions of the Procedure”(1 ). Our upper reference limit (URL) study used a total of 768 fresh hepa-rin-plasma samples from healthy individuals, which were collected at four different centers and tested with the VITROS Troponin I assay to establish a reference interval for healthyindividuals and to validate the product claims in the Package Insert and Instructions For Use. No samples were excluded because of hemolysis, and only two samples (0.25%) were above the URL of 0.08 g/L (ng/mL). The incidence of hemolyzed sam-ples in Dr. Hawkins’ study appears to be higher than our experience based on our customer service records. A hemoglobin concentration of 1000 mg/L (100 mg/dL) causes substantial discoloration of the sam-ple, which can be easily observed by most laboratory technicians and therefore flagged for potential inter-ferences. We recommend that customers continue to use the cutoffs stated in our labeling for the VITROS Tropo-nin I, i.e., 0.08 g/L as the URL and 0.4 g/L as the cutoff for acute myocardial infarction. Use of the cutoff of 0.22 g/L suggested by the author may lead to false nega-tives, which are clearly less desir-able from a medical point of view than the false positives that may result from a small number of greatly hemolyzed samples that have not been excluded by good laboratory practice