• Home
  • Search Results
  • Alternative calibration strategies for the clinical laboratory: application to nortriptyline therapeutic drug monitoring.

Alternative calibration strategies for the clinical laboratory: application to nortriptyline therapeutic drug monitoring.

Clinical chemistry (2013-02-22)
Matthew T Olson, Autumn Breaud, Robert Harlan, Nkechinyere Emezienna, Sabitha Schools, Alfred L Yergey, William Clarke

The addition of a calibration curve with every run is both time-consuming and expensive for clinical mass spectrometry assays. We present alternative calibration strategies that eliminate the need for a calibration curve except as required by laboratory regulations. We measured serum nortriptyline concentrations prospectively in 68 patients on 16 days over a 2-month period using a method employing calibration schemes that relied on the measurement of the response ratio (RR) corrected by the response factor (RF), i.e., a measurement of the RR for an equimolar mixture of the analyte and internal standard. Measurements were taken with contemporaneous RF (cRF) measurements as well as sporadic RF (sRF) measurements. The measurements with these alternative calibration schemes were compared against the clinical results obtained by interpolation on a calibration curve, and those differences were evaluated for analytical and clinical significance. The differences between the values measured by cRF and sRF calibration and interpolation on a calibration curve were not significant (P = 0.088 and P = 0.091, respectively). Both the cRF- and sRF-based calibration results demonstrated a low mean bias against the calibration curve interpolations of 3.69% (95% CI, -15.8% to 23.2%) and 3.11% (95% CI, -16.4% to 22.6%), respectively. When these results were classified as subtherapeutic, therapeutic, or supratherapeutic, there was categorical agreement in 95.6% of the cRF calibration results and 94.1% of the sRF results. cRF and sRF calibration in a clinically validated liquid chromatography-tandem mass spectrometry assay yields results that are analytically and clinically commensurate to those produced by interpolation with a calibration curve.

Product Number
Product Description

Nortriptyline hydrochloride, ≥98% (TLC), powder
Nortriptyline hydrochloride solution, 1.0 mg/mL in methanol (as free base), ampule of 1 mL, certified reference material, Cerilliant®
Nortriptyline hydrochloride, European Pharmacopoeia (EP) Reference Standard

Social Media

LinkedIn icon
Twitter icon
Facebook Icon
Instagram Icon


Research. Development. Production.

We are a leading supplier to the global Life Science industry with solutions and services for research, biotechnology development and production, and pharmaceutical drug therapy development and production.

© 2021 Merck KGaA, Darmstadt, Germany and/or its affiliates. All Rights Reserved.

Reproduction of any materials from the site is strictly forbidden without permission.