Analytical Considerations When Developing an LC-MS/MS Method for More than 30 Analytes

A New Broad-Spectrum Drug Screen for 127 Analytes by LC-MS/MS

BACKGROUND

Broad-spectrum drug screening is offered by many clinical laboratories to support investigation of possible drug exposures. The traditional broad-spectrum drug screen employed at our laboratory utilizes several different analytical platforms, thus requiring relatively high volumes of sample and a cumbersome workflow. Here we describe the development and validation of a consolidated broad-spectrum drug screen assay designed to qualitatively detect 127 compounds in urine (Ur) and serum/plasma (S/P) samples.

METHODS

An LC-MS/MS method was developed using the Ultivo LC-MS/MS and designed to be qualitative with a 1-point calibration curve and 50% to 150% controls. Sample preparation included the addition of 122 internal standards (IS) followed by mixed-mode strong cation exchange solid-phase extraction and reverse-phase chromatographic separation on a biphenyl column.

RESULTS

For the method described herein, ≥ 95% of analytes in urine and serum control samples had a CV of ≤20% for total imprecision. Accuracy testing included 46 external controls and demonstrated 99.9% accuracy. Method comparison studies to quantitative testing are discussed. The high level of coverage of the analytes with a stable isotope-labeled IS (SIL-IS) helped normalize for matrix effects when significant ion suppression (>25%) was present. Analyte stability in the matrix, the impact of potentially interfering compounds, and method ruggedness were demonstrated. Method limitations include limited detection of glucuronidated drugs and potential cross-contamination with samples at very high concentrations (>>100 × cutoff).

CONCLUSIONS

The broad-spectrum drug screen method developed here qualitatively detected 127 drugs and select metabolites. This method could be used to support investigations of possible drug exposures in a clinical setting.

Review of the Use of Liquid Chromatography-Tandem Mass Spectrometry in Clinical Laboratories: Part II-Operations

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is increasingly utilized in clinical laboratories because it has advantages in terms of specificity and sensitivity over other analytical technologies. These advantages come with additional responsibilities and challenges given that many assays and platforms are not provided to laboratories as a single kit or device. The skills, staff, and assays used in LC-MS/MS are internally developed by the laboratory, with relatively few exceptions. Hence, a laboratory that deploys LC-MS/MS assays must be conscientious of the practices and procedures adopted to overcome the challenges associated with the technology. This review discusses the post-development landscape of LC-MS/MS assays, including validation, quality assurance, operations, and troubleshooting. The content knowledge of LC-MS/MS users is quite broad and deep and spans multiple scientific fields, including biology, clinical chemistry, chromatography, engineering, and MS. However, there are no formal academic programs or specific literature to train laboratory staff on the fundamentals of LC-MS/MS beyond the reports on method development. Therefore, depending on their experience level, some readers may be familiar with aspects of the laboratory practices described herein, while others may be not. This review endeavors to assemble aspects of LC-MS/MS operations in the clinical laboratory to provide a framework for the thoughtful development and execution of LC-MS/MS applications.

Ritalinic acid in urine: Impact of age and dose

Objectives

The objective of this work was to study the results of urine drug testing for ritalinic acid (RA), the major urinary metabolite of methylphenidate (MP) (e.g., Ritalin®). The impact of age from 4 to 65 years old and older on median levels of RA was investigated as well as potential variations in pH, specific gravity and creatinine content of the patient urine samples.

Design and Methods

Samples from patients who were 1) prescribed MP and found to be positive for RA, 2) prescribed MP but found to be negative for RA and 3) not prescribed MP but tested positive for RA were examined by liquid chromatography – mass spectrometry/mass spectrometry (LC-MS/MS) for RA concentration. The levels of RA were examined for median and average levels and further normalized and transformed to reveal a near gaussian distribution.

Results

Over 20,000 samples from patients who were prescribed MP were examined for this work. Analysis of these data for a subset of patients prescribed MP and testing positive for RA revealed statistically different median values of RA for school age patients of 6 years old through 17 years old from adult patients 18 through 64 years old. Another 6751 samples were positive for RA without a prescription but were not included in the overall assessment of these data.

Conclusions

While not clear as to the reason, these data indicate that school age children under the age of 18 have much higher levels of RA than adult patients. These results can be used to estimate “normal” levels of RA in these chronically dosed populations.

Impact of the Opioid Epidemic on Drug Testing

BACKGROUND

This review provides a description of how the opioid epidemic has impacted drug testing.

METHODS

Four major service areas of drug testing were considered, including emergency response, routine clinical care, routine forensics, and death investigations.

RESULTS

Several factors that the opioid epidemic has impacted in drug testing are discussed, including specimens, breadth of compounds recommended for testing, time to result required for specific applications, analytical approaches, interpretive support requirements, and examples of published practice guidelines.

CONCLUSIONS

Both clinical and forensic laboratories have adapted practices and developed new testing approaches to respond to the opioid epidemic. Such changes are likely to continue evolving in parallel with changes in both prescription and nonprescription opioid availability and use patterns, as well as emerging populations that are affected by the "waves" of the opioid epidemic.