Volume 44, Issue 4

Remarkable advances in instrument technology, automation and computer science have greatly simplified many aspects of previously tedious tasks in laboratory diagnostics, creating a greater volume of routine work, and significantly improving the quality of results of laboratory testing. Following the development and successful implementation of high-quality analytical standards, analytical errors are no longer the main factor influencing the reliability and clinical utilization of laboratory diagnostics. Therefore, additional sources of variation in the entire laboratory testing process should become the focus for further and necessary quality improvements. Errors occurring within the extra-analytical phases are still the prevailing source of concern. Accordingly, lack of standardized procedures for sample collection, including patient preparation, specimen acquisition, handling and storage, account for up to 93% of the errors currently encountered within the entire diagnostic process. The profound awareness that complete elimination of laboratory testing errors is unrealistic, especially those relating to extra-analytical phases that are harder to control, highlights the importance of good laboratory practice and compliance with the new accreditation standards, which encompass the adoption of suitable strategies for error prevention, tracking and reduction, including process redesign, the use of extra-analytical specifications and improved communication among caregivers.

The clinical relevance of brain natriuretic peptide (BNP) and N-terminal (NT)-proBNP assays as a diagnostic tool and prognostic marker in patients with cardiovascular diseases has recently been confirmed. However, several studies demonstrated variation of intra-individual BNP concentrations of >30% (ranging from 30% to 50%) with reference change values at the 95% confidence interval (i.e., the estimated critical difference) ranging from 99% to 130% in healthy subjects and heart failure patients. According to this estimated confidence interval, only a great variation in plasma BNP levels should be considered significant in an individual patient (for example, a decrease of >50% or an increase of more than two-fold). Many recent clinical studies have demonstrated that BNP variations below this estimated critical difference could also have clinical relevance. Like the concentration of other neuro-hormones, levels of plasma BNP fluctuate widely and rapidly along with heart rhythm and blood pressure variations in response to physiological stimuli. However, biological variation of BNP should not be interpreted strictly as random fluctuation around a homeostatic set point, as assumed by the common model used in all studies on biological variation of BNP reported in the literature. These results cannot be directly transferred to clinical practice. While awaiting more accurate studies, we suggest that variations of plasma BNP three-fold greater than the analytical imprecision should be considered as potentially relevant from a physiological and clinical point of view.

This article summarizes the literature on current definition, suggested pathogenetic mechanisms and the role of laboratory assessment in the differential diagnosis of hepatorenal syndrome (HRS) from other causes of renal disease that may arise during hepatic cirrhosis and some diseases affecting both liver and kidney. It should be remembered that the main theory suggested for the pathogenesis of HRS is the arterial vasodilation hypothesis of portal hypertension, ending in type 1 and type 2 HRS, but there is no consensus supporting either mechanism as a solid theory for initiation of HRS pathogenesis to date. No laboratory test can firmly establish a diagnosis of HRS, which is mainly based on the absence of any specific cause of renal failure. Laboratory and ultrasonographic tests based on non-invasive techniques are being investigated as possible diagnostic approaches.

Background : In clinical laboratories, many test results such as low-density lipoproteins can be calculated using the results of specifically measured tests. However, quality control programs deal with only measured tests and there is no quality control procedure for calculated tests. I aimed to modify the Levey-Jennings chart for calculated tests as part of a total quality system. Methods : I developed a method using a Taylor series expansion and alternative equations to obtain the standard deviation of calculated tests and then prepared Levey-Jennings charts for these tests. Results : Preparation of Levey-Jennings charts for low-density lipoproteins (and other calculated tests) was simple, and using this chart increased the reliability of calculated test results. Conclusion : Checking only measured tests by quality control procedures before reporting patient results may be inadequate. Preparation of Levey-Jennings charts for calculated tests as part of total quality management will increase the reliability of test results.

Background : Cigarette smoking, a cardiovascular risk factor leading to oxygen free radical formation, is involved in the development of serious pathological conditions. On the other hand, a healthy diet and adequate supplementation can help prevent many diseases. The aim of our study was to evaluate in healthy light smokers the effects of supplementation with mixed fruit and vegetable juice powder concentrate on homocysteine metabolism and oxidative status. Methods : In this pilot study, 32 healthy volunteers, 16 light smokers and 16 non-smokers, on twice daily supplementation were monitored at time zero and after 30days. Plasma homocysteine, and serum vitamin B 12 and folate concentrations were measured by immunoenzymatic assays; reactive oxygen species, total antioxidant capacity and thiol groups by spectrophotometric methods; and total and free malondialdehyde concentrations by gas chromatography-mass spectrometry with isotopic dilution. Results : Baseline free malondialdehyde concentrations were significantly higher in smokers than in non-smokers and normalised after 30-day supplementation. Baseline results for all the other parameters remained unchanged after supplementation, with no significant differences between smokers and non-smokers. Conclusion : This is the first study showing a significant decrease in free malondialdehyde levels in light smokers after 1-month phytonutrient supplementation.

Background : The exponentially moving average (EWMA) rule for internal quality control is a well-known type of control rule in industry. Here, the power of the EWMA rule is evaluated to outline the potential of this type of control rule in clinical chemistry. Methods : Using simulations, the power of the EWMA rule was explicitly compared with that of commonly used rules in clinical chemistry. The type I error levels were standardized to common values to achieve unbiased comparisons. Results : For small to moderately large errors (systematic errors up to 2–3 standard deviations), the EWMA rule outperforms simple rules ( N =1) and multi-rules ( N =2–6). For example, for a systematic error of 2s, the EWMA rule equivalent to the 1 3s rule has a power of 0.30, whereas the 1 3s rule only displays a power of approximately 0.15. For N =4, comparison was carried out with the 1 3s /2 2s /R 4s /4 1s rule. Here the common type I error level is 0.017. At all error levels, the EWMA rule is superior to the multi-rule. For example, given a 1s systematic error, the EWMA rule has a power (0.4) of twice the value of the multi-rule (0.2). Conclusion : The EWMA rule is an efficient control rule with regard to systematic errors that should be considered for general application in the field of clinical chemistry.

Two multi-component scores (Fibrotest ® and Actitest ® ) have been proposed to evaluate liver fibrosis or necro-inflammatory lesions as an alternative to liver biopsy. This approach requires standardization of alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT) determinations. For this purpose, ALT and GGT values were assigned to a multi-enzyme material using the appropriate primary reference procedure. This material was used as a common calibrator for sera from 20 patients with viral hepatitis. Measurements were carried out in 11 laboratories, using their own automated routine methods and compared to results obtained using the primary reference procedure. The expression of results in multiples of the upper reference limit worsened the inter-laboratory variation for both enzymes. The multi-enzyme material was commutable for ALT and GGT determination carried out with six analytical systems. Common calibration significantly improved inter-laboratory consistency, which finally reached 1.8% and 3.3% for ALT and GGT, respectively. For each enzyme, it also permitted the retention of a common reference interval for a set of calibrated methods and the improvement of inter-laboratory coherency of Fibrotest ® and Actitest ® scores.

Background : We evaluated the measurement of length of sedimentation reaction in blood (LSRB) by TEST 1 and compared the results with those for the Westergren and Sed Rate Screener 100 (SRS 100) methods. Methods : LSRB was measured in 113 paired blood samples. Results : TEST 1 correlated significantly with the Westergren (r=0.94) and SRS 100 (r=0.90) methods with low bias (−0.29 and −1.92mm/h, respectively) and limits of agreement (−14.5 to 13.9, and −23.4 to 19.6mm/h, respectively). Hematocrit (Htc) correlated negatively with LSRB in TEST 1 (r=−0.54) and SRS 100 (r=−0.53) only in samples with high Htc (≥35%). The bias and limits of agreement between TEST 1 and Westergren in samples with low (−1.46 and −22.3 to 19.3mm/h) and high (0.43 and −7.29 to 8.14mm/h) Htc were comparable to those between SRS 100 and Westergren (1.83 and −27.2 to 30.9mm/h for low, 0.71 and −7.27 to 8.70mm/h for high Htc samples). Total protein and fibrinogen correlated similarly with LSRB in both TEST 1 (r=0.23 and 0.48, respectively) and SRS 100 (r=0.30 and 0.51, respectively). Conclusions : The findings suggested that TEST 1 is a reliable, precise and accurate system for measurement of LSRB in clinical laboratories with high workload.

The influence of interference by hemolysis, icterus and lipemia on the results of routine chemistries may lead to wrong interpretations. The H-, I- and L-indices that can be measured by the Beckman LX-20 instrument (Beckman Coulter) in serum or plasma samples are a reliable semi-quantitative measure of the size of these interferences. A survey carried out in 16 Dutch clinical laboratories on the use of these indices demonstrated that in several of these laboratories, the influence of interferences is largely underestimated. Therefore, a multicenter study was carried out in which we examined the interference of hemolysis, icterus and lipemia on 32 analytes. On the basis of biological variation, we decided on cutoff indices above which analytically significant interference exists. We found analytically significant interference by hemolysis, icterus or lipemia, in 12, 7 and 15 of the 32 analytes studied, respectively. Flagging of results on the basis of analytically significant interference, however, results in too many clinically insignificant comments. On the basis of clinical significance, we conclude that significant interference by hemolysis, icterus or lipemia is present in only 5, 6 and 12 of the analytes studied, respectively. Use of the cutoff indices presented here facilitates optimal use of the LX-20 indices to prevent reporting of wrong results due to interference.

Background : The CA 125 antigen is a large (200–1000kDa) glycoprotein, present within normal and benign ovarian tissue. We evaluated the analytical performance of the newly available Beckman Coulter OV-Monitor (CA 125 antigen) immunoassay on the Beckman Coulter UniCel™ DxI 800 analyzer. Methods : The evaluation was performed according to NCCLS recommendations. Results : The lowest level of CA 125 antigen detectable was 0.374U/mL. Serial dilution of two pooled CA 125 antigen-rich samples provided a linear response (p<0.0001). For total CV% the following results were obtained: pool sera, 11.7U/mL (2.70%), 56.3U/mL (2.41%), 108.43U/mL (2.31%); and QC sera, 29.4U/mL (2.57%), 101.1U/mL (3.26%). Comparison of the OV-Monitor on the UniCel™ DxI 800 showed linear regression values of r=0.961 vs. the Bayer ADVIA Centaur system and r=0.981 vs. the Abbott AxSYM system. Conclusion : Considering the limited number of serum samples analyzed, our data indicate that the Beckman Coulter OV-Monitor immunoassay has excellent analytical performance and shows satisfactory correlation with automated immunoassays on the Abbott AxSYM and Bayer ADVIA Centaur systems. It is easy to perform, accurate and suitable for measurements in routine clinical laboratories.

Background : Increased homocysteine (Hcy) blood levels are correlated with vascular and neurological problems. The aim of our study was to investigate erythrocyte membrane Na + ,K + -ATPase and Mg 2+ -ATPase activities in patients with methylenetetrahydrofolate reductase ( MTHFR ) 677 C→T genotype. Methods : Blood was obtained from 25 patients before and after folic acid supplementation and from controls (n=30) once. Plasma folate, vitamin B 12 and total antioxidant status (TAS) were measured using commercial kits, Hcy was determined by HPLC and membrane enzyme activities were measured spectrophotometrically. Results : Mg 2+ -ATPase remained unaltered. Membrane Na + ,K + -ATPase activity was remarkably increased in patients (0.77±0.06μmolPi/h × mg protein) and decreased to normal levels (0.52±0.05μmolPi/h × mg protein; p<0.001) after therapy. TAS did not differ significantly before and after treatment. Hcy levels were significantly higher before therapy (25.4±2.8μmol/L) than levels after therapy (12.1±2.0μmol/L; p<0.001) and in controls (10.5±2.5μmol/L, p<0.001). In vitro, L-phenylalanine (Phe) reversed to normal the stimulated enzyme from patients before therapy. In addition, Phe incubation of the Hcy activated membrane Na + ,K + -ATPase from controls resulted in restoration of its activity, whereas L-alanine (Ala) incubation protected the enzyme from Hcy activation. Conclusions : The increased membrane Na + ,K + -ATPase activity may be due to high -SH group Hcy levels. In vitro, Phe reversed the increase in enzyme activity induced by Hcy in controls, as well as the stimulated membrane enzyme in untreated patients. Ala protected the enzyme from Hcy action.

The aim of the study was to determine serum levels of selected matrix metalloproteinases (MMPs) and their natural inhibitors (TIMPs) in the acute phase of different stroke types subdivided according to the Oxfordshire Community Stroke Project (OCSP) classification and the possibility of discriminating stroke types according to their levels. The study included 126 patients with acute stroke within the first 24h of symptom onset, and 124 healthy volunteers. The stroke group had lower MMP-2 concentrations and MMP-2/TIMP-2 ratios (p<0.001) but higher TIMP-2 (p<0.001) than controls. The level of MMP-9 and the MMP-9/TIMP-1 ratio were higher in patients with total anterior circulation infarct (TACI) than in patients with other stroke subtypes according to OCSP classification (p=0.0019, p=0.0065, respectively) or in controls (p<0.0001, p=0.0024, respectively). A negative correlation of MMP-2 levels with MMP-9 and MMP-9/TIMP-1 ratio was recorded in all stroke subtypes except for TACI. Receiver operating characteristic analysis showed similar discriminating power for MMP-9 levels and Barthel index in the differential diagnosis of TACI. High MMP-9/TIMP-1 ratio (odds ratio 3.263) was associated with TACI. Our results demonstrate that the MMP-9/TIMP-1 ratio may provide information to help in assessing stroke patients in the future as a baseline biomarker of infarct extent.

Background : DNA sequencing has markedly changed the nature of biomedical research. Large-scale sequencing projects have generated several millions of potential polymorphisms widespread in the human genome requiring validation and incorporation into screening panels. As a consequence, high-throughput analysis of these variants in different populations of interest is now the cornerstone of structural genomics. Pyrosequencing is a versatile technique allowing an easy 96-well typing format. However, every polymorphism requires a specific labeled primer to generate a single-stranded DNA fragment containing the region of interest. Methods : We describe how with an adjusted primer stoichiometry we can standardize the labeling of every amplicon with a single biotinylated universal primer (BM13S). Results : We circumvent the need for specific biotinylated primers for each single-nucleotide polymorphism (SNP) under study. As an example, we assessed this novel protocol by genotyping three SNPs mapping calpain-10, caveolin-1 and CYP19A1. Conclusion : The present approach represents an alternative to standard pyrosequencing protocols, since it requires a single biotinylated primer that is suitable for each SNP under study.

Background : We examined antibodies against 60-, 65- and 70-kDa heat shock proteins (HSPs) in paediatric healthy individuals, patients with juvenile idiopathic arthritis (JIA) and those undergoing allogeneic stem-cell transplantation for various malignant and non-malignant diseases. Methods : Western blotting and ELISA were used to examine HSP-directed humoral immune responses. Results : Using ELISA we detected anti-Hsp60, -Hsp65 and -Hsp70 IgG antibodies in patient sera before, during and after conditioning and at all post-transplant times, as well as in JIA patients and controls. Western blotting showed positivity for anti-Hsp60 and anti-Hsp65 antibodies in all samples with a HSP concentration of 0.5μg/lane. However, anti-Hsp70 antibodies were not detected at all when both sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE were used, except for one JIA patient, for whom a positive signal was only achieved in native PAGE when Hsp70 was increased to 2μg/lane and serum dilution decreased to 1:10. Conclusion : Western blotting is convenient for the detection of anti-Hsp60 and anti-Hsp65 antibodies, but it is not sensitive enough for the detection of anti-Hsp70 antibodies. ELISA, which is more sensitive, might be preferentially used to screen anti-Hsp60, -Hsp65 and -Hsp70 antibodies in sera of children with various disorders.

Background : Given the role of folate in many disorders, intracellular distribution of folate vitamers is of potential clinical importance. In particular, accumulation of non-methyltetrahydrofolates due to altered partitioning of folate metabolism at the level of methylenetetrahydrofolate is of interest. Methods : We describe a positive-electrospray liquid chromatography tandem mass spectrometry (LC-MS/MS) method that allows determination of erythrocyte folate vitamer distribution by accurately measuring both 5-methyltetrahydrofolate (5-methylTHF) and non-methyl folate vitamers. Whole blood lysates are deconjugated in ascorbic acid solutions, deproteinized, purified using folate-binding protein affinity columns, concentrated by solid-phase extraction (SPE) and evaporation, and separated on a C18 column within 6min. Results : The limit of quantification for both 5-methylTHF and non-methylTHF was 0.4nmol/L (signal-to-noise >10). Intra- and inter-assay CVs for 5-methylTHF were 1.2% and 2.8%, respectively. Intra- and inter-assay CVs for non-methylTHF as a group were 1.6% and 1.5%, respectively. Recovery results were 97–107%. We measured 8–72% non-methyl folate vitamers in volunteers (n=5) with the methylenetetrahydrofolate reductase ( MTHFR ) 677 TT genotype. Concentrations ranged from 117 to 327nmol/L and 23 to 363nmol/L for 5-methylTHF and non-methylTHF vitamers, respectively. We measured 0–2% non-methylTHF vitamers in MTHFR 677 CC genotype volunteers. In addition, we found that storage of whole-blood samples in ascorbic acid at low pH resulted in 53–90% loss of the non-methylTHF fraction. Conclusion : This LC-MS/MS method accurately determines erythrocyte 5-methylTHF and non-methyl folate vitamers.

Background : Oxidative stress is said to strongly influence the neurological recovery of patients following a severe head injury. Estimation of the markers of oxidative stress in the blood of such patients can hence aid in predicting the prognosis of head injury. Methods : Erythrocyte thiobarbituric acid-reactive substances (TBARS) and plasma ceruloplasmin (CP) levels were estimated in 24 severe head-injury patients on days 1, 7 and 21 of the post-traumatic period and compared with levels in 25 healthy age- and sex-matched controls. These parameters reflecting oxidative stress status were related to the Glasgow Coma Scale (GCS) scores of patients noted at the same time points of the study period. Results : Lipid peroxidation as indicated by increased levels of erythrocyte TBARS remained significantly elevated in severe head injury patients compared to controls on day 1 (p<0.001), day 7 (p<0.001) and 21 (p<0.001) of the post-traumatic period. Plasma CP levels remained significantly elevated (p<0.001) at these three time points compared to controls. The significant decrease in lipid peroxidation products (p<0.01) and significant increase in CP levels (p<0.001) on day 21 compared to day 1 in head injury patients correlated well with the significant improvement in GCS scores of patients on day 21 compared to day 1 (p<0.05). Conclusion : The above results could account for the adaptation of the study patients to severe oxidative stress, as evidenced by their clinical recovery trend during the study period.

The aim of the present work was to compare in a supposed healthy population of 680 subjects several algorithms for positive selection of urine samples requiring microscopic examination for erythrocytes and leukocytes after screening by automated test-strip measurement and particle counting on a Sysmex UF-50™ flow cytometer. Four strategies have been formulated and the sensitivity, specificity, positive predictive value, negative predictive value, false positive rate, false negative rate, and microscopic review rate were measured. The strategy combining test strip analysis and automated counting on all samples, followed by microscopic examination of only discordant samples gave the best results. When the two methods of haematuria screening were in agreement (91% of samples), the false negative rate for microscopy was 1.1%, with a false positive rate of 0.8%, sensitivity of 66% and specificity of 99%, and the results are acceptable without any other examination. When the two methods of haematuria screening were discrepant, visual microscopic analysis was necessary to obtain definitive results. For leukocyturia screening, 80% of results were in agreement by test strip and automatic sediment urinalysis, with only ten results considered as false negatives (1.8%) and four as false positives (0.7%). Agreement was good and the other criteria were good (sensitivity 79%, specificity 99%). On conflicting samples, there was no agreement between methods and microscopic analysis was essential. The benefit of such an algorithm would be optimisation of the workflow without any loss of sensitivity and specificity at the expense of a two-fold increase in cost.

The aims of this study were to determine circulating choline status and its relationship to circulating levels of S-100β protein and neuron-specific enolase, biochemical markers of cerebral injury and cognitive decline, after coronary artery bypass grafting (CABG) surgery. Preoperatively, patients scheduled for off-pump or on-pump CABG surgery had serum concentrations of 12.0±0.2 and 11.7±0.4μmol/L free choline and 2640±65 and 2675±115μmol/L phospholipid-bound choline, respectively. Serum free and bound choline levels decreased by 22–37% or 34–47% and 16–36% or 31–38% at 48h after off-pump or on-pump surgery, respectively. Serum S-100β and neuron-specific enolase increased from preoperative values of 0.083±0.009 and 6.3±0.2μg/L to 0.405±0.022 and 11.4±0.8μg/L, respectively, at 0h postoperatively and remained elevated for 48h after off-pump surgery. Serum free and bound choline concentrations were inversely correlated with the concentrations of S-100β (r=−0.798; p<0.001 and r=−0.734; p<0.001) and neuron-specific enolase (r=−0.840; p<0.001 and r=−0.728; p<0.001). In conclusion, CABG surgery induces a decline in serum free and phospholipid-bound choline concentrations. The decreased serum choline concentrations were inversely correlated with the elevated levels of circulating cerebral injury markers. Thus, a decline in circulating choline may be involved in postoperative cognitive decline.

Two commercially available drug-screening assays were evaluated: the Roche kinetic interaction of microparticles in solution (KIMS) assay and the Microgenics cloned enzyme donor immunoassay (CEDIA). Urine samples from known drug-abuse patients were analyzed for amphetamines, barbiturates, benzodiazepines, benzoylecgonine, cannabinoids, LSD, methadone and opiates. Samples with discordant findings for the two assays were analyzed by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/electron capture detection (GC/ECD). Amphetamines showed 96.0% concordant results, with two false positive findings by CEDIA, three by KIMS and a further two false negatives by KIMS. Barbiturates showed 99.4% concordant results, with one false negative by KIMS. Benzodiazepines showed 97.4% concordant results, with two false negatives by KIMS (cutoff 100μg/L, CEDIA cutoff 300 μg/L). Benzoylecgonine showed 17.8% concordant positive and 82.2% concordant negative results and no false finding by either assay. Cannabinoids showed 99.3% concordant results, with one sample negative by KIMS at a cutoff of 50μg/L and positive by CEDIA (cutoff 25μg/L). For LSD, 6.7% of findings were not in agreement. Methadone showed 97.5% concordant results, with two false positives by CEDIA, and one false positive and one false negative by KIMS. Opiates showed 96.9% concordant results, with no false KIMS results, but four false positives by CEDIA. The results indicate that the agreement of the CEDIA and KIMS results for the eight drugs is rather good (93.3–100%).

Background : Endogenous ligands of cannabinoid receptors (endocannabinoids), in particular anandamide (arachidonylethanolamide), have been recognized as being of crucial importance in a variety of physiological functions. Plasma concentrations of anandamide have been measured in a number of investigations; however, discrepant data on “normal” anandamide plasma concentrations were reported. Since this might be caused by pre-analytical variables, we investigated the impact of different sample handling conditions on measured plasma anandamide concentrations. Methods : Blood samples were taken from healthy volunteers in EDTA- or heparin-containing tubes; whole blood samples were kept at +4°C, room temperature, or 37°C, respectively, for up to 120min before obtaining plasma by centrifugation. Plasma anandamide concentrations were measured by an isotope-dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Results : A marked time- and temperature-dependent increase in plasma anandamide concentrations ex vivo was observed in both EDTA- and heparin-containing tubes. Mean anandamide concentrations approximately doubled when EDTA samples were kept at 4°C for 60min before centrifugation [immediately centrifuged, 1.3μg/L (SD 0.3μg/L); 2.8μg/L (SD 0.5μg/L) after storage for 60min; n=12). After storage of heparinized whole-blood samples for 120min at 37°C, a mean plasma anandamide concentration of 11.9μg/L (SD 1.8μg/L) was found. In cell-free plasma, no increase in anandamide concentrations was found. Conclusion : Anandamide is released from blood cells ex vivo at a very high rate; therefore, strictly standardized pre-analytical protocols have to be applied for plasma anandamide determination.

Background : Splanchnic ischemia plays a major role in the development of organ failure during septic shock. Plasma D-lactate has been proposed as a better marker of splanchnic hypoperfusion than L-lactate. We studied the prognostic ability of plasma D- and L-lactate levels. Methods : A prospective study was performed in an intensive care unit and included patients with septic shock. Two samples for plasma D- and L-lactate determination were collected: the first within 6h after the patient met the criteria for septic shock (day 1) and the second 24h later (day 2). Results : In univariate analysis, day 1 plasma D- and L-lactate values were associated with 28-day mortality. For plasma D- and L- lactate, the area under the receiver operating characteristic curve was 0.68±0.09 and 0.84±0.07 on day 1 (p=0.09), and 0.74±0.10 and 0.90±0.07 on day 2 (p=0.06), respectively. In survivors, D-lactate levels decreased between day 1 and day 2 (p=0.03), but L-lactate did not (p=0.29). In septic shock patients, plasma D- and L-lactate levels reliably discriminate between survivors and non-survivors. The prognostic ability of plasma L-lactate was better than that of plasma D-lactate. Conclusion : A rapid decrease in plasma D-lactate during the course of septic shock could indicate reduced 28-day mortality.

Background : Sirolimus is widely used as an immunosuppressant, along with calcineurin inhibitors. Because of its variable pharmacokinetics and narrow therapeutic range, therapeutic drug monitoring of sirolimus is critical to optimize its therapeutic effect and to minimize toxicity. Although liquid chromatography/tandem mass spectrometry is considered the method of choice, the technical and financial challenges of this method are obstacles to its use. A microparticle enzyme immunoassay on the Abbott IMx has recently been reintroduced to the clinical diagnostic market. Methods : We evaluated this immunoassay using high-performance liquid chromatography/tandem mass spectrometry as the reference method. Precision and carryover were evaluated using an expanded CLSI EP10-A2 protocol. Linearity was studied by serial dilution of high-level whole blood samples, and clinical utility was demonstrated by correlation with the reference method using 56 de-identified pediatric patient samples. Results : The total imprecision was less than 12% across the concentrations tested. The method was linear from 2.6 to 31nM. The immunoassay showed a mean positive bias of 11.5% in patient specimens relative to high-performance liquid chromatography/mass spectrometry (p<0.001), with a correlation coefficient (R) of 0.953. Conclusion : We conclude that the reintroduced immunoassay is useful for therapeutic drug monitoring of sirolimus.

No Abstract available