Not T too! False elevations in high-sensitivity cardiac troponin T (hs-TnT) following specimen transport.

Though false elevations attributed to preanalytical specimen handling have been widely reported for Troponin I (TnI), Troponin T (TnT) has appeared more robust to falsely elevated Tn. We describe reproducible false elevations in high sensitivity TnT (hs-TnT) in specimens after courier transport in plasma separator tubes (PST) off-site for testing. Hs-TnT was measured under 5 different conditions: 1) at collection location (N = 24); 2) after transport upright in racks (N = 66); 3) after transport with no control over tube agitation (N = 69); 4) on transported aliquots (N = 84); or 5) immediately after transport with no control over tube agitation (N = 16), followed by keeping the specimen upright and re-measuring at 1hr, 2hr, 4hr, and 20-24hrs (N = 6). To assess the degree of discrepancy, plasma from the original PST was aliquotted, re-centrifuged, potential debris removed, and hs-TnT re-measured. 43% of PST specimens collected offsite and transported with no control over tube agitation had clinically significant false elevations of hs-TnT which subsequently decreased following aliquotting and re-centrifugation (median decrease = 9.9 ng/L). Onsite testing or transported aliquots demonstrated no discrepancy. After being kept upright, discrepant specimens were not different from re-centrifuged aliquots by 4hrs (p = 0.6141, repeated measures ANOVA with Dunn's multiple comparisons). Clinically significant false elevations of hs-TnT occurred in approximately 40% of separated PSTs that were transported in containers where specimens are transported with no control over tube agitation. This interference does not occur if plasma is aliquoted or if hs-TnT is tested at the collection site. In order to prevent these false elevations, and their potential patient impact on the diagnosis of acute myocardial infarction, specimens for hs-TnT measurement should be aliquoted at the collection location prior to transport.

Rising above helium: A hydrogen carrier gas chromatography flame ionization detection (GC-FID) method for the simultaneous quantification of toxic alcohols and ethylene glycol in human plasma specimens.

Here we validate a GC, Flame Ionization Detection (GC-FID), liquid injection method using hydrogen as a carrier gas combining analysis of toxic volatile alcohols (VA): methanol, ethanol, isopropanol, acetone, as well as glycols, ethylene glycol (EG) and propylene glycol (PG), in a single method. METHODOLOGY: 200 µL of calibrator, QC, or patient specimen were deproteinized with 400 µL of acetonitrile containing internal standards (10 mmol/L N-propyl alcohol for VA and 2.5 mmol/L 1,2-butanediol for glycols). GC-FID analysis using hydrogen carrier gas and nitrogen makeup gas utilized an Agilent 7890 system equipped with Agilent 7683 liquid autosampler on a 30 m × 530 µm RTX-200 fused silica column. Method validation included repeatability, recovery, carryover, linearity, lower limit of quantification (LLOQ), accuracy, selectivity and measurement uncertainty. RESULTS: The 8.3 min from injection to injection reduced time of analysis by 45% over a previously reported method using Helium carrier gas with no loss in resolution. Within-run and Between-run variability were ≤1.4% and ≤6.8% respectively. Recovery was 100% within a 95% confidence interval. Carryover was negligible for all but EG. LLOQ was <1 mmol/L for all analytes. The upper range of linearity was 120 mmol/L for methanol, ethanol and isopropanol, 100 mmol/L for acetone and 50 mmol/L for EG. Analytes demonstrated acceptable accuracy and measurement uncertainty using College of American Pathologists (CAP) criteria. Toluene can cause a false positive EG, while benzene, xylene and 1,3 butanediol can cause false negative EG. CONCLUSIONS: Converting from Helium to Hydrogen carrier gas benefits patient care through a reduction in turnaround time and provides a cost savings to the laboratory.