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Limit of Quantitation

Meaning

The Limit of Quantitation (LOQ) is a fundamental analytical chemistry parameter that precisely defines the lowest concentration of an analyte, such as a circulating hormone or metabolite, that can be reliably measured and reported with an acceptable, predetermined level of accuracy and precision. In clinical endocrinology, the LOQ is a critical determinant of a laboratory test’s utility, particularly when measuring the very low concentrations of biologically active free hormones like estradiol or free testosterone. Results falling below this threshold are typically reported as undetectable or “less than LOQ,” indicating that the numerical value is not trustworthy for clinical decision-making. This metric is essential for maintaining the scientific rigor and clinical relevance of hormonal testing.