Characterization of the second conserved domain in the heme uptake protein HtaA from Corynebacterium diphtheriae.

HtaA is a heme-binding protein that is part of the heme uptake system in Corynebacterium diphtheriae. HtaA contains two conserved regions (CR1 and CR2). It has been previously reported that both domains can bind heme; the CR2 domain binds hemoglobin more strongly than the CR1 domain.

A Library of Rare α1-Antitrypsin (AAT) Variant Phenotypes to Aid in the Diagnosis of AAT Deficiency.

Objectives: α1-Antitrypsin (AAT) deficiency is a hereditary disorder due to defective production of the serine protease inhibitor, AAT, which can cause lung and liver diseases. Severity of disease depends particularly on the phenotypic representation of AAT variants in the patient.

Methods: In this study, we present determination of seven common and nine rare variant phenotypes of AAT using pediatric samples collected in Texas Children's Hospital to address the knowledge gap in the identification of rare variants.

Multiple calibrator measurements improve accuracy and stability estimates of automated assays.

Objectives: The effects of combining multiple calibrations on assay accuracy (bias) and measurement of calibration stability were investigated for total triiodothyronine (TT3), vitamin B12 and luteinizing hormone (LH) using Beckman Coulter's Access 2 analyzer.

Methods: Three calibration procedures (CC1, CC2 and CC3) combined 12, 34 and 56 calibrator measurements over 1, 2, and 3 days. Bias was calculated between target values and average measured value over 3 consecutive days after calibration.

Evaluation of the Lipid Interference for Siemens BN ProSpec Cystatin C Assay Using Pediatric Samples.

Endogenous interferents (lipids, hemoglobin and bilirubin) are a common cause of pre-analytical laboratory errors. We evaluated the effect of lipemia on Siemens cystatin C assay using pediatric samples. Lipemic samples were prepared by adding various concentrations of triglycerides into low and high cystatin C sample pools.

Heme Binding by Corynebacterium diphtheriae HmuT: Function and Heme Environment.

The heme uptake pathway (hmu) of Corynebacterium diphtheriae utilizes multiple proteins to bind and transport heme into the cell. One of these proteins, HmuT, delivers heme to the ABC transporter HmuUV. In this study, the axial ligation of the heme in ferric HmuT is probed by examination of wild-type (WT) HmuT and a series of conserved heme pocket residue mutants, H136A, Y235A, and M292A.

Assessment of liver function tests on Piccolo Xpress point of care chemistry analyzer in a pediatric hospital.

Objectives: Point of care testing (POCT) contributes to diagnosis and monitoring with fast testing time and easily performed assays. We evaluated the Abaxis Piccolo Xpress point of care chemistry analyzer using the Liver Panel Plus discs for our pediatric patient population at Texas Children's Hospital.

Design And Methods: Analytical performance was evaluated for precision and linearity using quality control materials and commercially available verification samples.

Validation of the procalcitonin (PCT) assay: Experience in a pediatric hospital.

Objectives: Procalcitonin (PCT) is a potential early biomarker used to differentiate sepsis from systemic inflammation. Serial PCT measurement is useful in reducing the duration of antibiotic exposure without increasing treatment failure. Our aim was to establish and evaluate an automated quantitative PCT assay at Texas Children's Hospital.

Evaluation of Beckman Coulter DxI 800 immunoassay system using clinically oriented performance goals.

Objectives: We evaluated the analytical performance of 24 immunoassays using the Beckman Coulter DxI 800 immunoassay systems at Mayo Clinic, Rochester, MN for trueness, precision, detection limits, linearity, and consistency (across instruments and reagent lots).

Methods: Clinically oriented performance goals were defined using the following methods: trueness-published desirable accuracy limits, precision-published desirable biologic variation; detection limits - 0.1 percentile of patient test values, linearity - 50% of total error, and consistency-percentage test values crossing key decision points.