Common causes of hyperammonemia include liver failure (hepatocyte destruction and reduced urea cycle enzymes), drug reactions (e.g., inhibition of the urea cycle by valproic acid), hemolytic disease ...(release of ammonia from red blood cells), gastrointestinal bleeds (increased ammonia generation due to microbial catabolism of hemoglobin), or urea cycle disorders (defective or decreased urea cycle enzymes) (1 ). ...c) samples collected for ammonia testing would be considered STAT priority to reduce processing and analysis time. Because of their central importance in clinical laboratories, centrifuges and their operating procedures should be carefully evaluated to minimize preanalytical errors (10).
Radioactive reagents are used in most assays for measurement of 1,25-dihydroxyvitamin D 1,25(OH)(2)D. We evaluated a 1,25(OH)(2)D enzyme immunoassay (EIA) from IDS Ltd. that uses solid-phase ...immunoextraction and colorimetric detection and compared results to those of the thymus radioreceptor assay (RRA) for 1,25(OH)(2)D.
We collected serum samples (n = 145) representing an even distribution (0-200 pmol/L) of 1,25(OH)(2)D concentrations and Vitamin D External Quality Assessment Scheme (DEQAS) proficiency survey samples from 2004 surveys (n = 15) and stored them at -20 degrees C. We analyzed all samples with both EIA and RRA methods. We calculated imprecision using 5 QC samples in quadruplicate in each run (n = 6), including both pooled patient material used for QC with the RRA and QC material included in the EIA reagent set. We evaluated calibration stability by analyzing calibrators from different lots on the same plate and determining if calculated sample values drifted significantly.
Deming linear regression between IDS EIA and RRA methods yielded slope 1.25 (95% CI 1.13-1.37), y-intercept -3 (95% CI -18 to 12), R(2) = 0.74. DEQAS proficiency survey samples for 2004 were all within 30% of the all-methods-trimmed mean. Imprecision CVs were 12%-16% within-run and 15%-20% between-run.
We find no evidence of inferiority to the classic calf-thymus receptor assay for 1,25(OH)(2)D and no disadvantage in the results generated by the IDS EIA using samples from the major proficiency survey for 1,25(OH)(2)D. According to the product insert, however, the IDS EIA underestimates 1,25(OH)(2)D(2) compared with the D(3) form.
There is limited information about the effects of instituting CLSI Document C56A recommended workflows for the automated detection of hemolysis, lipemia and icterus (HIL) in different clinical ...laboratories and patient populations. We describe a process to develop and tailor automated reporting rules that are appropriate for the local laboratory population.
Automated decision algorithms were generated and applied to 2 high volume labs serving community and hospital populations. Proposed rules were applied to the datasets offline to predict the outcomes, and then were further optimized prior to implementation.
Introduction of automated serum indices decreased HIL flagging compared to manual flagging. Hemolysis flagging was the greatest in all 3 patient populations, and was successfully reduced for LD, CK and AST by optimized rules that incorporated both the H-index result and the analyte result. Changes in flagging rates were also patient population specific, particularly for icterus which was a problem in hospitalized populations but not in the community. Overall, concordance between manual and automated flagging methods was very low in both laboratories.
We demonstrate that flagging algorithms may not be universally transferable due to lab specific and population specific factors and demonstrate the benefits of local, a priori testing of algorithms prior to implementation.
•A process to develop and test automated serum indices decision rules is outlined.•This process was modeled in 2 laboratories serving 3 patient populations.•Serum indices decision algorithms need to be tailored to laband patient population.
Sex-specific diagnostic cut-offs may improve the test characteristics of high-sensitivity troponin assays for the diagnosis of myocardial infarction (MI). The objective of this study was to quantify ...test characteristics of sex-specific cut-offs of a single, high-sensitivity cardiac troponin T (hs-cTnT) assay for 7-day MI in patients with chest pain.
This observational cohort study included consecutive emergency department (ED) patients with suspected cardiac chest pain from four Canadian EDs who had an hs-cTnT assay performed within 60 minutes of ED arrival. The primary outcome was MI at 7 days. We quantified test characteristics (sensitivity, negative predictive value NPV, likelihood ratios and proportion of patients ruled out) for multiple combinations of sex-specific, rule-out cut-offs. We calculated the net reclassification index compared to universal rule-out cut-offs.
In 7,130 patients (3,931 men and 3,199 women), the 7-day MI incidence was 7.38% among men and 3.78% among women. Optimal sex-specific cut-offs (<8 ng/L for men and <7 ng/L for women) had a 98.5% sensitivity for MI and ruled out MI in 55.8% of patients. This would enable an absolute increase in the proportion of patients who were able to be ruled out with a single hs-cTnT of 13.2% to 22.2%, depending on the universal rule-out concentration used as a comparator.
Sex-specific hs-cTnT cut-offs for ruling out MI at ED arrival may improve classification performance, enabling more patients to be safely ruled out at ED arrival. However, differences between sex-specific and universal cut-off concentrations are within the variation of the assay, limiting the clinical utility of this approach. These findings should be confirmed in other data sets.
Clinical analysis of volatile alcohols (i.e. methanol, ethanol, isopropanol, and metabolite acetone) and ethylene glycol (EG) generally employs separate gas chromatography (GC) methods for analysis. ...Here, a method for combined analysis of volatile alcohols and EG is described.
Volatile alcohols and EG were extracted with 2:1 (v:v) acetonitrile containing internal standards (IS) 1,2 butanediol (for EG) and n-propanol (for alcohols). Samples were analyzed on an Agilent 6890 GC FID. The method was evaluated for precision, accuracy, reproducibility, linearity, selectivity and limit of quantitation (LOQ), followed by correlation to existing GC methods using patient samples, Bio-Rad QC, and in-house prepared QC material.
Inter-day precision was from 6.5–11.3% CV, and linearity was verified from down to 0.6mmol/L up to 150mmol/L for each analyte. The method showed good recovery (~100%) and the LOQ was calculated to be between 0.25 and 0.44mmol/L. Patient correlation against current GC methods showed good agreement (slopes from 1.03–1.12, and y-intercepts from 0 to 0.85mmol/L; R2>0.98; N=35). Carryover was negligible for volatile alcohols in the measuring range, and of the potential interferences tested, only toluene and 1,3 propanediol interfered. The method was able to resolve 2,3 butanediol, diethylene glycol, and propylene glycol in addition to the peaks quantified.
Here we describe a simple procedure for simultaneous analysis of EG and volatile alcohols that comes at low cost and with a simple liquid–liquid extraction requiring no derivitization to obtain adequate sensitivity for clinical specimens.
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•This method combines ethylene glycol and volatile alcohol analyses into one run.•The method shows clean background, good sensitivity, and high reproducibility.•The method employs low cost liquid injection and flame ionization detection.•Rapid and simple extraction is easily adaptable to other clinical laboratories.•The method is validated according to CLSI guidelines for clinical application.
We have investigated the influence of Ki-ras oncogene on Met/hepatocyte growth factor (HGF) receptor signaling in human carcinoma cells. The model system used in these studies included the DLD-1 ...colon cancer cell line with a mutated Ki-ras allele, and the DKO-4 cell line generated from DLD-1, with its mutant Ki-ras allele inactivated by targeted disruption. These cell lines were transduced with cDNAs of either active Met receptor or dominant negative Met receptor. As compared to the DLD-1 cells, constitutive overexpression of Met receptor in this cell line (DLD-1-Met) resulted in increased tumorigenicity in SCID mice. In contrast, overexpression of Met in DKO-4 cells (DKO-4-Met) that have lost oncogenic Ras activity demonstrated suppressed tumorigenicity with respect to the parent DKO-4 cell line. Tumors formed by the DLD-1-Met cells showed increased levels of mitogen-activated protein kinase (MAPK) and lower levels of apoptosis compared to the DKO-4-Met tumors. Overexpression of the dominant negative Met receptor cDNA decreased the Met phosphorylation levels in both DLD-1 and DKO-4 cells, but only suppressed tumorigenicity in the DKO-4 cell line. In vitro, HGF stimulation of DLD-1 cells resulted in a prolonged duration of MAPK activation, while DKO-4 cells exhibited a rapid attenuation of MAPK phosphorylation. The results suggest that Ki-ras mutations and HGF signaling cooperate to enhance tumor growth by increased duration of MAPK activation and decreased apoptosis in human carcinoma cells.
Background: Radioactive reagents are used in most assays for measurement of 1,25-dihydroxyvitamin D 1,25(OH).sub.2D. We evaluated a 1,25(OH).sub.2D enzyme immunoassay (EIA) from IDS Ltd. that uses ...solid-phase immunoextraction and colorimetric detection and compared results to those of the thymus radioreceptor assay (RRA) for 1,25(OH).sub.2D. Methods: We collected serum samples (n = 145) representing an even distribution (0-200 pmol/L) of 1,25(OH).sub.2D concentrations and Vitamin D External Quality Assessment Scheme (DEQAS) proficiency survey samples from 2004 surveys (n = 15) and stored them at -20degreesC. We analyzed all samples with both EIA and RRA methods. We calculated imprecision using 5 QC samples in quadruplicate in each run (n = 6), including both pooled patient material used for QC with the RRA and QC material included in the EIA reagent set. We evaluated calibration stability by analyzing calibrators from different lots on the same plate and determining if calculated sample values drifted significantly. Results: Deming linear regression between IDS EIA and RRA methods yielded slope 1.25 (95% CI 1.13-1.37), y-intercept -3 (95% CI -18 to 12), R.sup.2 = 0.74. DEQAS proficiency survey samples for 2004 were all within 30% of the all-methods-trimmed mean. Imprecision CVs were 12%-16% within-run and 15%-20% between-run. Conclusions: We find no evidence of inferiority to the classic calf-thymus receptor assay for 1,25(OH).sub.2D and no disadvantage in the results generated by the IDS EIA using samples from the major proficiency survey for 1,25(OH).sub.2D. According to the product insert, however, the IDS EIA underestimates 1,25(OH).sub.2D.sub.2 compared with the D.sup.3 form.
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