Analysis of dicarboxylic acids by tandem mass spectrometry. High-throughput quantitative measurement of methylmalonic acid in serum, plasma, and urine.

Background: Methylmalonic acid (MMA) is a dicarboxylic acid whose concentration can be increased in blood and urine in patients with an inborn error of metabolism or vitamin B(12) deficiency. We developed a method for the selective analysis of dicarboxylic acids that exploits the high specificity of tandem mass spectrometry (MS/MS) and the substantial difference in fragmentation patterns of the isomers methylmalonic (MMA) and succinic acid (SA).

Methods: Dicarboxylic acids were extracted from samples with methyl-tert-butyl ether and derivatized with butanolic HCl to form dibutyl esters.

Interobserver and intraobserver variability in the cytologic diagnosis of normal and abnormal metaplastic squamous cells in pap smears.

Objective: Interoberver variability has important implications for patient care, diagnostic error and medical litigation. In the management of any cervical epithelial abnormality, its biologic significance as well as diagnostic reproducibility is very important. Interobserver variability has not been measured adequately for metaplastic squamous lesions.

ASCUS, mature metaplastic type. Cytologic diagnosis and follow-up.

Objective: To study the cytologic criteria for follow-up of mature metaplastic cells within the atypical squamous cells of undetermined significance (ASCUS) category.

Study Design: Squamous epithelial abnormalities between January 1994 and June 1997 at our institution totaled 2,632 and included squamous carcinoma (1), high grade squamous intraepithelial lesions (278), low grade squamous intraepithelial lesions (875) and ASCUS (1,478). From the ASCUS group, 134 (9.

Optimization and performance of a rapid gas chromatography-mass spectrometry analysis for methylmalonic acid determination in serum and plasma.

We have developed a rapid and sensitive GC-MS assay for methylmalonic acid determination in serum and plasma utilizing an anion exchange solid-phase extraction and trimethylsilyl derivatization. Each step of the procedure was optimized by the experimental design methods to assure the assay reliable performance. The limit of detection and limit of quantitation were 0.

Comparison of representative ranges based on U.S. patient population and literature reference intervals for urinary trace elements.

Reference intervals for trace elements are very hard to obtain because of the difficulty of defining a nonexposed reference population. However, representative ranges for trace elements obtained from a general patient population can provide useful information in interpreting laboratory results. We have used urine specimens submitted for trace metal analysis from patients residing in the United States to calculate representative ranges for 25 urinary trace elements, and to compare them to reference values taken from the literature.