Transportation and handling of blood samples prior to ammonia measurement in the real life of a large university hospital.

BACKGROUND: Hyperammonemia is neurotoxic and as such can be a medical emergency. Preanalytical factors greatly influence the blood ammonia concentration results. AIMS AND METHODS: Ammonia concentrations measured in the real life setting of a large hospital after pneumatic transport of blood samples and various time periods before centrifugation were compared to those based on the indications of the reagent manufacturer. In the same routine context, the effects of waiting times of centrifuged samples or after plasma storage at -20 °C and -80 °C were determined. RESULTS: Despite the pneumatic transport, the lead times for sample arrival to the lab were even longer than those recommended for their complete handling until ammonia assay. Ammonia concentration results were not affected by the pneumatic transport of blood samples and by waiting times up to a maximum of 1.75 h before their centrifugation and 1 h after centrifugation. Ammonia stability was superior when plasma was stored at -80 °C. CONCLUSION: Pneumatic transport and sample handling in the routine practice of our lab do not affect ammonia concentration results provided that waiting times are limited to 1.75 h before and 1 h after centrifugation and samples are kept cold. Otherwise, it is better to freeze plasma at -80 °C.

Wide-range CRP versus high-sensitivity CRP on Roche analyzers: focus on low-grade inflammation ranges and high-sensitivity cardiac troponin T levels.

Wide-range C-reactive protein (wr-CRP) has been proposed as an economical alternative to high-sensitivity C-reactive protein (hs-CRP) for the evaluation of low-grade inflammation-associated cardiovascular risk (LGI-CVR). Concomitant values of serum hs-CRP and plasma wr-CRP ≤5 mg/L, and high-sensitivity cardiac troponin T (hs-cTnT), all assayed on Roche Diagnostics analyzers over a 1.8-year period, were extracted from a hospital laboratory database. Hs-CRP and wr-CRP values were compared (Bland-Altman method; Deming's correlation), then separately classified into low (<1 mg/L), moderate (1-3 mg/L) and high (>3 mg/L) LGI-CVR ranges for agreement test (κ), assessed before and after Deming's regression-based adjustment of wr-CRP (Adj-wr-CRP). Wr-CRP and hs-CRP values were strongly correlated, with linearity, whether below 5 mg/L (n = 744; τ = 0.933; p < .001) or below 1 mg/L (n = 283; τ = 0.823; p < .001). Overall, wr-CRP values were lower than hs-CRP (mean bias: -0.11 ± 0.17 mg/L). Agreement was good, with 8.1% of wr-CRP values misclassified compared to hs-CRP (κ: 0.874), and weakly improved after regression-based adjustment (7.7% reclassified values; κ: 0.881). Lowering the Adj-wr-CRP cutoff of the moderate LGI-CVR subrange from 1.0 to 0.9 mg/L resulted in an almost perfect agreement (3.2% reclassified data; κ: 0.950). Hs-cTnT concentration was positively associated with hs-CRP, wr-CRP, and Adj-wr-CRP (p < .001). Within each LGI-CVR subrange, hs-cTnT medians were similar regardless of the hs-CRP, wr-CRP or Adj-wr-CRP used for risk classification. Based on hs-cTnT, this study supports the use of wr-CRP as a low-cost alternative to hs-CRP for cardiovascular risk evaluation.

Plasma cystatin C as a marker for estimated glomerular filtration rate assessment in HIV-1-infected patients treated with dolutegravir-based ART.

Objectives: Inhibition of the organic cation transporter-2 renal tubule transporter by dolutegravir leads to serum creatinine increase. Serum cystatin C is a non-organic cation transporter-2-dependent marker, possibly enabling glomerular filtration rate (GFR) estimation under dolutegravir. Our goal was to evaluate the changes in creatinine- and cystatin C-based estimated GFR values before and after dolutegravir initiation. Methods: Creatinine and cystatin measurements were carried out on frozen plasma samples from HIV-1-infected patients, before and after dolutegravir initiation, between October 2016 and March 2017 at Pitié-Salpêtrière Hospital. CKD-EPI equations were used to estimate mean GFR from creatinine and cystatin C values. Variations were analysed by paired t-test. Results: Forty-four patients were included [median age = 48 years (IQR 36-58) and median CD4 count = 592 cells/mm3 (IQR 388-728)], including 6 ART-naive patients and 38 on switch strategies [72% with viral load <50 copies/mL and median ART duration = 13 years (IQR 5-20)]. Before dolutegravir initiation (median time = 41 days), 19 patients (43%) had creatinine-based estimated GFR <90 mL/min/1.73 m2 and 11 (25%) had cystatin C-based estimated GFR <90 mL/min/1.73 m2. After dolutegravir initiation, serum creatinine values significantly increased (+8.6 µmol/L, 95% CI +5.8; +11.4, P < 0.001) and associated estimated GFR significantly decreased (-7.7 mL/min/1.73 m2, 95% CI -10.4; -5.1, P < 0.001). In contrast, there was no significant change in cystatin C value variation and associated estimated GFR. The same results were observed regardless of renal function at baseline. Conclusions: Creatinine values increased after dolutegravir initiation, whereas no change was observed for cystatin C values. Use of cystatin C may enable better understanding of plasma creatinine fluctuations after dolutegravir initiation, particularly in high-risk renal patients.

High-Sensitivity Cardiac Troponin T: a Preanalytical Evaluation.

BACKGROUND: Little is known about the effects of preanalytical conditions on high-sensitivity cardiac troponin T (hs-cTnT) concentrations. METHODS: Variations of hs-cTnT concentrations were evaluated under the following preanalytical conditions: 1) serum vs. lithium-heparin (Li-Hep) plasma, with or without separator gel; 2) centrifugation time (15-minutes vs. 10-minutes) and speed (1467 to 3756 g); 3) stability in Li-Hep plasma at room temperature and +4 degrees C for 4 days and at -80 degrees C for up to 12 months, for three concentrations; 4) four freeze-thaw cycles at -20 degrees C and -80 degrees C, for three concentrations. RESULTS: No significant changes were found regarding the type of blood collection tube, the centrifugation, and storage conditions. Minor decreases were observed after four freeze-thaw cycles at -20 degrees C (< 6.5%) and -80 degrees C (< 3.4%). CONCLUSIONS: High-sensitivity cardiac troponin T may be considered as not impacted by usual preanalytical conditions, thus strengthening its reliability in laboratory practice and clinical research.

Stability of Routine Biochemical Analytes in Whole Blood and Plasma From Lithium Heparin Gel Tubes During 6-hr Storage.

BACKGROUND: The stability of biochemical analytes has already been investigated, but results strongly differ depending on parameters, methodologies, and sample storage times. We investigated the stability for many biochemical parameters after different storage times of both whole blood and plasma, in order to define acceptable pre- and postcentrifugation delays in hospital laboratories. METHODS: Twenty-four analytes were measured (Modular® Roche analyzer) in plasma obtained from blood collected into lithium heparin gel tubes, after 2-6 hr of storage at room temperature either before (n = 28: stability in whole blood) or after (n = 21: stability in plasma) centrifugation. Variations in concentrations were expressed as mean bias from baseline, using the analytical change limit (ACL%) or the reference change value (RCV%) as acceptance limit. RESULTS: In tubes stored before centrifugation, mean plasma concentrations significantly decreased after 3 hr for phosphorus (-6.1% [95% CI: -7.4 to -4.7%]; ACL 4.62%) and lactate dehydrogenase (LDH; -5.7% [95% CI: -7.4 to -4.1%]; ACL 5.17%), and slightly decreased after 6 hr for potassium (-2.9% [95% CI: -5.3 to -0.5%]; ACL 4.13%). In plasma stored after centrifugation, mean concentrations decreased after 6 hr for bicarbonates (-19.7% [95% CI: -22.9 to -16.5%]; ACL 15.4%), and moderately increased after 4 hr for LDH (+6.0% [95% CI: +4.3 to +7.6%]; ACL 5.17%). Based on RCV, all the analytes can be considered stable up to 6 hr, whether before or after centrifugation. CONCLUSION: This study proposes acceptable delays for most biochemical tests on lithium heparin gel tubes arriving at the laboratory or needing to be reanalyzed.

Hemolysis indexes for biochemical tests and immunoassays on Roche analyzers: determination of allowable interference limits according to different calculation methods.

OBJECTIVES: To determine the hemolysis interference on biochemical tests and immunoassays performed on Roche Diagnostics analyzers, according to different maximum allowable limits. DESIGN AND METHODS: Heparinized plasma and serum pools, free of interferences, were overloaded by increasing amounts of a hemoglobin-titrated hemolysate. This interference was evaluated for 45 analytes using Modular(®) and Cobas(®) analyzers. For each parameter, the hemolysis index (HI) corresponding to the traditional ± 10% change of concentrations from baseline (± 10%Δ) was determined, as well as those corresponding to the analytical change limit (ACL), and to the reference change value (RCV). Then, the relative frequencies distribution (% RFD) of hemolyzed tests performed in a hospital laboratory over a 25-day period were established for each HI as allowable limit. RESULTS: Considering the ± 10%Δ, the analyte concentrations enhanced by hemolysis were: Lactate dehydrogenase (LDH), aspartate aminotransferase (AST), folate, potassium, creatine kinase, phosphorus, iron, alanine aminotransferase, lipase, magnesium and triglycerides, decreasingly. The analyte concentrations decreased by hemolysis were: Haptoglobin, high-sensitive troponin T and alkaline phosphatase. Over the 25-day period, the % RFD of tests impacted more than 10%Δ by hemolysis were < 7% for LDH; < 5% for AST, folates and iron; and < 1% for the other analytes. Considering the ACL, HI were lower, giving % RFD substantially increased for many analytes, whereas only four analytes remain sensitive to hemolysis when considering RCV. CONCLUSION: This study proposes new HI based on different allowable limits, and can therefore serve as a starting point for future harmonization of hemolysis interference evaluation needed in routine laboratory practice.

Lipoprotein-associated phospholipase A2 during the hyperacute stage of ischemic and hemorrhagic strokes.

BACKGROUND: The objectives of the study were to compare lipoprotein-associated phospholipase A2 (Lp-PLA2) levels in a prospective cohort including both ischemic and hemorrhagic strokes at the hyperacute phase, and to investigate if these levels were associated with stroke severity. MATERIALS AND METHODS: Lp-PLA2 mass and activity were measured during the first 6 hours of symptom onset before any therapeutic intervention. The Lp-PLA2 level was analyzed by comparing the mass and activities in ischemic strokes and spontaneous intracerebral hemorrhages (ICH). Correlations between Lp-PLA2 levels and clinical scores as well as stroke volumes were made. The temporal evolution of Lp-PLA2 during the first week was analyzed in ischemic stroke patients. RESULTS: Lp-PLA2 mass was higher in ICH than in ischemic stroke (P = .001). Lp-PLA2 activity at admission correlated with initial and follow-up stroke volume in ICH (P = .003 and P = .004, respectively) but not in ischemic stroke. None of the measurements correlated with clinical severity for either diagnosis. Lp-PLA2 mass decreased during the first week after the use of statins in ischemic stroke, whereas the activity remained stable. CONCLUSIONS: Lp-PLA2 mass is higher in ICH compared with ischemic stroke during the hyperacute stage. Lp-PLA2 activity is associated with stroke volume in ICH but not in ischemic stroke. This suggests that Lp-PLA2 mass and activity could provide different information in the hyperacute stage of stroke.