Concentrations of Trace Elements in Hemodialysis Patients: A Prospective Cohort Study.

BACKGROUND: Low concentrations and excessive concentrations of trace elements have been commonly reported in hemodialysis patients, but available studies have several important limitations. STUDY DESIGN: Random sample of patients drawn from a prospective cohort. SETTING & PARTICIPANTS: 198 incident hemodialysis patients treated in 3 Canadian centers. MEASUREMENTS: We used mass spectrometry to measure plasma concentrations of the 25 elements at baseline, 6 months, 1 year, and 2 years following enrollment in the cohort. We focused on low concentrations of zinc, selenium, and manganese and excessive concentrations of lead, arsenic, and mercury; low and excessive concentrations of the other 19 trace elements were treated as exploratory analyses. Low and excessive concentrations were based on the 5th and 95th percentile plasma concentrations from healthy reference populations. RESULTS: At all 4 occasions, low zinc, selenium, and manganese concentrations were uncommon in study participants (≤5.1%, ≤1.8%, and ≤0.9% for zinc, selenium, and manganese, respectively) and a substantial proportion of participants had concentrations that exceeded the 95th percentile (≥65.2%, ≥74.2%, and ≥19.7%, respectively). Almost all participants had plasma lead concentrations above the 95th percentile at all time points. The proportion of participants with plasma arsenic concentrations exceeding the 95th percentile was relatively constant over time (9.1%-9.8%); the proportion with plasma mercury concentrations that exceeded the 95th percentile varied between 15.2% and 29.3%. Low arsenic, platinum, tungsten, and beryllium concentrations were common (>50%), as were excessive cobalt, manganese, zinc, vanadium, cadmium, selenium, barium, antimony, nickel, molybdenum, lead, and chromium concentrations. CONCLUSIONS: There was no evidence that low zinc, selenium, or manganese concentrations exist in most contemporary Canadian hemodialysis patients. Some patients have excessive plasma arsenic and mercury concentrations, and excessive lead concentrations were common. These findings require further investigation.

Challenges in harmonizing integrated healthcare network laboratories: multi-center evaluation of the hCG5 assay.

BACKGROUND: Beckman Coulter recently introduced a new hCG assay manufactured for the Access 2 and DxI platforms. This assay is the first to use the 5th International Standard (5th IS) as its primary calibration material. Clinical laboratories are required to validate the method performance before testing and reporting patient results. METHODS: Beckman Coulter Access 2 instruments (n=41) across Kaiser Permanente Northern California were evaluated for their performance characteristics using the hCG5 reagent. Precision, linearity, dilution verification, and patient sample comparisons were performed on each instrument. RESULTS: The assay was linear up to 1350IU/L. Intra-day and inter-day precision ranged from 1.0%-3.3% and 1.8-7.3%, respectively, for the low QC material (mean concentration 4.6IU/L). Percent bias between the previous assay (hCG2) and the hCG5 assay was 3.2 to 22.7% for hCG concentrations <1000IU/L and -2.9 to 30% for concentrations >1000IU/L. On board and manual dilutions agreed within 15% following proper adjustment of the instrument dilution factor. CONCLUSIONS: Achieving Access 2 inter-instrument agreement on specimens needing dilutions (hCG>1350IU/L) requires validation of the on board dilution factor. Laboratories should use QC material above the linear range to monitor instrument dilution accuracy and precision.

Challenges in harmonizing integrated healthcare network laboratories: Multi-center evaluation of the AccuTnI+3 troponin assay.

BACKGROUND: Beckman Coulter has recently introduced a new troponin assay manufactured for the Access2 and DxI platforms, releasing it under the name AccuTnI+3. Clinical laboratories are required to validate method performance before testing and reporting patient results. METHODS: Beckman Coulter Access 2 instruments (n=42) across Kaiser Permanente Northern California were evaluated for their performance characteristics using the AccuTnI+3 reagent. Precision, linearity, and patient sample comparisons were performed on each instrument. Limit of the blank (LOB), limit of detection (LOD), limit of quantitation (LOQ), serum plasma comparisons, and specimen stability were evaluated using a single instrument. RESULTS: The assay was linear from 0-100,000ng/L. The LOB, LOD and LOQ were determined to be 5, 8 and 20ng/L, respectively. Interday precision on the low QC (mean concentration 41ng/L) ranged from 3.0% to 14.2%. The bias observed between the former assay (AccuTnI) and the AccuTnI+3 was comparable to the inter-instrument bias for either assay. Non-uniform distribution was observed in the precision and inter-instrument/inter-assay comparisons among the instruments evaluated. CONCLUSIONS: The AccuTnI and AccuTnI+3 troponin assays are equivalent across the analytical measuring range. There was no significant difference at the medical decision point. No changes in patient results are anticipated. However, the assay-independent inter-instrument bias observed is an important consideration for harmonization efforts.