Calibration Practices in Clinical Mass Spectrometry: Review and Recommendations

Abstract

Background: Calibration is a critical component for the reliability, accuracy, and precision of mass spectrometry measurements. Optimal practice in the construction, evaluation, and implementation of a new calibration curve is often underappreciated. This systematic review examined how calibration practices are applied to liquid chromatography-tandem mass spectrometry measurement procedures.Methods: The electronic database PubMed was searched from the date of database inception to April 1, 2022. The search terms used were "calibration," "mass spectrometry," and "regression." Twenty-one articles were identified and included in this review, following evaluation of the titles, abstracts, full text, and reference lists of the search results.Results: The use of matrix-matched calibrators and stable isotope-labeled internal standards helps to mitigate the impact of matrix effects. A higher number of calibration standards or replicate measurements improves the mapping of the detector response and hence the accuracy and precision of the regression model. Constructing a calibration curve with each analytical batch recharacterizes the instrument detector but does not reduce the actual variability. The analytical response and measurand concentrations should be considered when constructing a calibration curve, along with subsequent use of quality controls to confirm assay performance. It is important to assess the linearity of the calibration curve by using actual experimental data and appropriate statistics. The heteroscedasticity of the calibration data should be investigated, and appropriate weighting should be applied during regression modeling.Conclusions: This review provides an outline and guidance for optimal calibration practices in clinical mass spectrometry laboratories.

Probing Liquid Chromatography–Tandem Mass Spectrometry Response Dynamics and Nonlinear Effects for Response Level Defined Calibration Strategies with Simple Methods To Expand Linear Dynamic Ranges

“…This is due, in part, to the shifting applicable concentration range caused by LC–MS/MS response dynamics. While previous studies have attempted to develop quadratic regression calibration strategies by analyzing empirical observations of residual error distributions across different approaches, − these methods primarily focus on concentration ranges rather than response levels. Consequently, their effectiveness may be compromised due to shifts in the response profile at various sensitivity levels, as depicted in Figure .…”

From fundamentals in calibration to modern methodologies: A tutorial for small molecules quantification in liquid chromatography–mass spectrometry bioanalysis

“…In contrast to EC, the in-sample approach is distinguished by an analytical calibration obtained directly in the study sample. The standard addition method (SAM) is probably the most established IsC methodology because it is used in many fields, such as foods, environment or forensic toxicology, where different analytical matrices are considered [127,128]. In this section, two other approaches that aim to simplify the quantification stages by LC-MS are also discussed.…”

Integrating a Multiple Isotopologue Reaction-Monitoring Technique and LC-MS/MS for Quantitation of Small Molecules: Ten Mycotoxins in Cereals as an Example

“…16,25 To counter these effects and rectify random errors during sample pretreatment and instrumental analysis, the introduction of a stable isotope internal standard (SIL-IS) to the sample proves effective, which achieves precise quantitative analysis. 16,18 To construct the ISCC, an SIL-IS is combined with the multiple isotopologue reaction-monitoring (MIRM) technology. 23,24,26,27 Here, the abundance of each MIRM is measured by LC-MS/MS, while the theoretical isotopic abundance of each MIRM channel is accurately calculated based on the isotopic distribution of its product ions and neutral loss groups.…”

“…Nevertheless, when confronted with the simultaneous quantification of an array of compounds, the MSCC method proves laborious and time-intensive, primarily due to the extensive preparation of working standard solutions. , The one-point calibration (OPC) method simplifies the procedure by requiring just a single measurement point; its drawback is evident, that is, a lack of a second calibration point to characterize the instrument’s dynamic response adequately. , Typically, the OPC method is more suitable when the sample’s analyte concentration closely aligns with the value of the concentrations generated in the OPC. In essence, the existing calibration strategies boast both advantages and limitations. , This underscores the pressing need for the development of a novel calibration curve strategy aimed at optimizing the analytical performance of LC-MS/MS, thereby amplifying the precision, accuracy, and efficiency of quantitative analytical methodologies.…”

“…In recent years, a novel calibration strategy based on isotopologue distribution has been proposed to enable the quantitation of peptide compounds with exceptional accuracy and throughput using LC-MS/MS. , Among these approaches, the in-sample calibration curve (ISCC) stands out as a particularly intriguing strategy, which eliminates the need for laborious preparation of the conventional MSCC by incorporating the calibration curve into each sample to be analyzed. − In LC-MS/MS analysis, matrix effects (MEs) pose an inescapable challenge. , To counter these effects and rectify random errors during sample pretreatment and instrumental analysis, the introduction of a stable isotope internal standard (SIL-IS) to the sample proves effective, which achieves precise quantitative analysis. , To construct the ISCC, an SIL-IS is combined with the multiple isotopologue reaction-monitoring (MIRM) technology. ,,, Here, the abundance of each MIRM is measured by LC-MS/MS, while the theoretical isotopic abundance of each MIRM channel is accurately calculated based on the isotopic distribution of its product ions and neutral loss groups. , With the ability to effectively counter MEs, minimize measurement errors during quantitative analysis, simplify the cumbersome preparation of traditional external calibration curves, and enhance analytical throughput, the ISCC strategy has garnered significant attention and successfully been applied in drug development and environmental analysis. ,,,− However, the ISCC strategy does exhibit notable limitations. The distribution of concentration points within the calibration curve is primarily constrained by the compound’s elemental composition, particularly its correlation with the number of carbon atoms. , In general, compounds with over 20 carbon atoms perform exceptionally well with the ISCC.…”