Investigation of saliva as an alternative matrix to blood for the biological monitoring of inorganic lead.

INTRODUCTION: Whole blood is the established matrix for biological monitoring of inorganic lead; however blood sampling is an invasive procedure. Saliva offers a potential non-invasive alternative. This study determines lead in whole blood and saliva. A novel method for saliva sampling and preparation is presented. METHODS: Paired blood and saliva samples were obtained from 105 occupationally exposed UK workers. Saliva was collected using a StatSure sampling device, and a nitric acid digestion step was incorporated. The utility of the device for this application was evaluated. Whole blood was obtained by venepuncture. Analyses were carried out by ICP-MS. RESULTS: The limit of detection for lead in saliva was 0.011 µg/L. Mean blank-corrected recovery from 10 µg/L spiked saliva was 65.9%. The mean result from blank saliva extracted through the StatSure device was 2.86 µg/L, compared to 0.38 µg/L by direct analysis. For the paired samples, median blood lead was 6.00 µg/dL and median saliva lead was 17.1 µg/L. Pearson's correlation coefficient for saliva lead versus blood lead was 0.457 (95% C.I. 0.291-0.596). CONCLUSIONS: ICP-MS analysis allows sensitive determination of lead in saliva with low limits of detection. The StatSure device is effective for high occupational exposures, but contamination from the device could confound lower-level measurements. Saliva would only be effective as a surrogate for whole blood for highly-exposed populations, although with further work it may have applications as a biomarker of recent exposure.

An investigation of normal urine with a creatinine concentration under the cutoff of 20 mg/dL for specimen validity testing in a toxicology laboratory.

In clinical and forensic toxicology laboratories, one commonly used method for urine specimen validity testing is creatinine concentration. In this study, workplace guidelines are examined to determine their relevance to forensic and clinical toxicology samples. Specifically, it investigates the occurrence of urine creatinine concentrations under 20 mg/dL and notes potential issues with factors influencing creatinine concentration by utilizing a simple, novel method consisting of cation-paring high-pressure liquid chromatography in tandem with ultraviolet detection to determine the creatinine concentration in 3019 donors. Of the 4227 sample population in this study, 209 (4.94%) were below the cutoff value of 20 mg/dL for dilute urine. Because there are many factors that can influence the urinary creatinine concentration, samples that have creatinine under the 20 mg/dL cutoff do not always implicate sample adulteration.