A calibration study can include concentrations below the method’s reported limit of quantification. That distinction matters when a laboratory report uses a number near the bottom of the range. Rao and colleagues examined desvenlafaxine and alprazolam using HPLC with ultraviolet detection in spiked human plasma.
The reported linear range began at 10 µg/mL for desvenlafaxine and 5 µg/mL for alprazolam. The calculated quantification limits were higher, at 14.365 and 5.730 µg/mL, respectively. The lower calibrator describes a concentration included in the linearity evaluation. The quantification limit addresses the lower boundary for reporting a quantitative result under the method’s criteria.
Compare the reported concentration and units with the laboratory’s validated reportable range. Then check the evidence for accuracy and precision near that concentration. This paper tested prepared plasma samples under specified conditions. The limits belong to that method and matrix, and a different laboratory or specimen needs its own performance evidence.