To the Editor:
I read with great interest the report by Eriksson et al. (1), discussing the existence of a frequently occurring blood component that interferes with immunoassays measuring cardiac troponin I (cTnI) by use of antibodies against epitopes in the central part of the molecule. As a main indicator of the assay accuracy, the authors studied the analytical recovery of a purified preparation of human cardiac ternary TnI-TnT-TnC complex (from HyTest Ltd., Turku, Finland) added to different samples obtained from healthy individuals and from patients with acute coronary syndrome, using assays that recognize different cTnI epitopes.
By definition, recovery refers to the ability of an analytical method to measure an analyte correctly when a known amount of it is added to authentic samples (2). Estimation of recovery can therefore be an effective means of obtaining accuracy information because it tests whether the method can measure the analyte in the presence of all other compounds contained in the matrices of authentic samples. Unfortunately, there were some pitfalls in the recovery experiments performed by Eriksson et al. (1) as the …
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