Clinical Validation of a 106-SNV MALDI-ToF MS Pharmacogenomic Panel

Clinical application of time-of-flight mass spectrometry nucleic acid detection technology in diagnosis of drug-resistant pulmonary tuberculosis

PURPOSE

This study aims to evaluate the clinical diagnostic value of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for tuberculosis and drug-resistant tuberculosis.

PATIENTS AND METHODS

Totally 201 pulmonary tuberculosis patients were recruited retrospectively. All patients underwent smear microscopy, Mycobacterium growth indicator tube (MGIT) 960 culture, loop-mediated isothermal amplification (LAMP) molecular testing, Xpert MTB/RIF (Xpert), and MassARRAY assay which is a MALDI-TOF MS based method.

RESULTS

Among the enrolled patients, 28.36 %, 43.78 %, 47.26 %, 64.68 %, and 85.57 % tested positive by smear, culture, LAMP, Xpert, and MALDI-TOF MS, respectively. MALDI-TOF MS had significantly higher detection rates than the other methods (All P < 0.05). In the 88 culture-positive patients, the positive detection rates for smear, LAMP, Xpert, and MALDI-TOF MS were 43.2 %, 68.2 %, 85.2 %, and 94.3 %, respectively; In 113 culture-negative cases, the positive rates for the above tests were 16.8 %, 31.0 %, 48.7 %, and 78.8 %, respectively. Among the 130 Xpert-positive cases, the positive rates for smear, culture, LAMP, and MALDI-TOF MS were 40.77 %, 57.7 %, 70.77 %, and 98.46 %, respectively; In the 71 Xpert-negative cases, the positive rates for above tests were 5.6 %, 18.3 %, 4.2 %, and 62.0 %, respectively. In the 61 rifampicin-resistant cases, the successful detection rate of MALDI-TOF MS (96.72 %) was significantly higher than that of Xpert (81.97 %) (P < 0.05). The concordance between MALDI-TOF MS and pDST for detecting resistance to 11 anti-tuberculosis drugs ranged from 83.0 % to 98.9 %.

CONCLUSION

Nucleic acid detection technology using time-of-flight mass spectrometry provides a powerful tool for the rapid diagnosis of tuberculosis and drug-resistant tuberculosis, with advantages of high sensitivity and reliability, warranting further promotion and application.

MALDI-TOF MS-based SNP assay used to determine the appropriate antidepression for Chinese patients

Medicine remains the preferred primary treatment for depression, although some patients show remarkable individual variations in achieving satisfactory clinical outcomes during medication. Genetic polymorphisms cause approximately 40 % of individual differences in treatment response. Therefore, this study aimed to develop a technique to identify single nucleotide polymorphisms (SNPs) associated with the metabolism, effectiveness, and side effects of antidepressant medications in Chinese patients. Bibliometrics was used to search literature related to "depression" and "SNP" in Web of Science. The obtained SNP information was screened using the PharmGKB database. By designing and optimizing primers and conducting a compound amplification system, a method was established based on MALDI-TOF MS to detect polymorphisms associated with the antidepressant drugs, including sertraline, fluoxetine, citalopram, escitalopram, venlafaxine, fluvoxamine, paroxetine, and mirtazapine. The accuracy and sensitivity of the established method were verified by Sanger sequencing. A total of 10,043 articles were screened from the database, and 46 SNPs with a mutation frequency of >1 % in Asian populations and annotated with relevant clinical drugs were extracted from the PharmGKB database. This method was compared with the results of Sanger sequencing, and the accuracy of the detection results was 100 %. The MALDI-TOF MS-based SNP assay developed in this study can be a fast, convenient and effective way for patients to find the right medication for themselves. Moreover, we found that this SNP assay holds the promise of being a potential reference tool for assessing individualised differences in drug efficacy, not only for screening the causes of poor antidepressant efficacy in patients after taking medication, but also for advising physicians to understand individualised differences in drug efficacy.

A comparative study of MassARRAY and GeneXpert assay in detecting rifampicin resistance in tuberculosis patients' clinical specimens

Objectives

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a potent tool for detecting drug resistance in tuberculosis (TB); however, concerns about its reliability have been raised. In this study, we assessed the reliability of MassARRAY (Sequenom, Inc.), which is a MALDI-TOF MS-based method, by comparing it to the well-established GeneXpert assay (Cepheid) as a reference method.

Methods

A retrospective study was conducted using laboratory data retrieved from Henan Chest Hospital (Zhengzhou, China). To ensure a rigorous evaluation, we adopted a comprehensive assessment approach by integrating multiple outcomes of the Xpert assay across various specimen types.

Results

Among the 170 enrolled TB cases, MassARRAY demonstrated significantly higher sensitivity (85.88%, 146 of 170) compared to the Xpert assay (76.62%, 118 of 154) in TB diagnosis (p < 0.05). The concordance in detecting rifampicin resistance between MassARRAY and the combined outcomes of the Xpert assay was 90%, while it was 97.37% (37 of 38) among smear-positive cases and 89.06% (57 of 64) among culture-positive cases. When compared to the phenotypic susceptibility outcomes of the 12 included drugs, consistency rates of 81.8 to 93.9% were obtained, with 87.9% for multiple drug resistance (MDR) identification.

Conclusion

MassARRAY demonstrates high reliability in detecting rifampicin resistance, and these findings may offer a reasonable basis for extrapolation to other drugs included in the test panel.

Potential Impact of Pharmacogenomic Single Nucleotide Variants in a Rural Caucasian Population

BACKGROUND

In the US adverse drug reactions (ADRs) are estimated to cause 100 000 fatalities and cost over $136 billion annually. A patient's genes play a significant role in their response to a drug. Pharmacogenomics aims to optimize drug choice and dose for individual patients by characterizing patients' pharmacologically relevant genes to identify variants of known impact.

METHODS

DNA was extracted from randomly selected remnant whole blood samples from Caucasian patients with previously performed complete blood counts. Samples were genotyped by mass spectrometry using a customized pharmacogenomics panel. A third-party result interpretation service used genotypic results to predict likely individual responses to frequently prescribed drugs.

RESULTS

Complete genotypic and phenotypic calls for all tested Cytochrome P450 isoenzymes and other genes were obtained from 152 DNA samples. Of these 152 unique genomic DNA samples, 140 had genetic variants suggesting dose adjustment for at least one drug. Cardiovascular and psychiatry drugs had the highest number of recommendations, which included United States Food and Drug Administration warnings for highly prescribed drugs metabolized by CYP2C19, CYP2C9, CYP2D6, HLA-A, and VKORC1.

CONCLUSIONS

Risk for each drug:gene pairing primarily depends upon the degree of predicted enzyme impairment or activation, width of the therapeutic window, and whether parent compound or metabolite is pharmacologically active. The resulting metabolic variations range from risk of toxicity to therapeutic failure. Pharmacogenomic profiling likely reduces ADR potential by allowing up front drug/dose selection to fit a patient's unique drug-response profile.

Target-allele-specific probe single-base extension (TASP-SBE): a novel MALDI-TOF-MS strategy for multi-variants analysis and its application in simultaneous detection of α-/β-thalassemia mutations

Single-nucleotide variants (SNVs) and copy number variations (CNVs) are the most common genomic variations that cause phenotypic diversity and genetic disorders. MALDI-TOF-MS is a rapid and cost-effective technique for multi-variant genotyping, but it is challenging to efficiently detect CNVs and clustered SNVs, especially to simultaneously detect CNVs and SNVs in one reaction. Herein, a novel strategy termed Target-Allele-Specific Probe Single-Base Extension (TASP-SBE) was devised to efficiently detect CNVs and clustered SNVs with MALDI-TOF-MS. By comprehensive use of traditional SBE and TASP-SBE strategies, a MALDI-TOF-MS assay was also developed to simultaneously detect 28 α-/β-thalassemia mutations in a single reaction system, including 4 α-thalassemia deletions, 3 HBA and 21 HBB SNVs. The results showed that all 28 mutations were sensitively identified, and the CNVs of HBA/HBB genes were also accurately analyzed based on the ratio of peak height (RPH) between the target allele and reference gene. The double-blind evaluation results of 989 thalassemia carrier samples showed a 100% concordance of this assay with other methods. In conclusion, a one-tube MALDI-TOF-MS assay was developed to simultaneously genotype 28 thalassemia mutations. This novel TASP-SBE was also verified a practicable strategy for the detection of CNVs and clustered SNVs, providing a feasible approach for multi-variants analysis with MALDI-TOF-MS technique.