Annals of Clinical Biochemistry最新文献

Background: Biomarkers in cerebrospinal fluid (CSF) are crucial for diagnosing, monitoring, and prognosing neurological disorders.Purpose: This study evaluates the impact of preanalytical variables, particularly container choice, on CSF protein measurements.Analysis: Using 30 CSF samples, we compared sterile, additive-free tubes and lithium heparin tubes without separator gel.Results: Protein levels were significantly elevated higher in heparin tubes (mean difference: 230.71 mg/dL, P < .001).Conclusions: This overestimation underscores the necessity of adhering to preanalytical protocols to avoid erroneous clinical interpretations and ensure accurate diagnostic outcomes.

BackgroundIron is ubiquitously distributed in biology, only a miniscule amount exists as free is capable of catalysing production of highly toxic reactive hydroxyl radicle. This free iron also called; labile iron, non-transferrin bound iron or catalytic iron (CI). CI is measured by bleomycin detectable iron assay. The assay as described originally was difficult to perform accurately and reproducibly due to variations of pH in the assay mixture and due to the lack of properly diluted iron standards.MethodsIn our laboratory we modified the assay for serum/plasma so that the variations of pH in assay medium were constantly between 7.4 and 7.6 using acid diluted iron standards by multiple treatments of Chelex resin which is alkaline.ResultsIntra assay CV for low, medium, and high levels of catalytic iron was 0.05%, 0.61% and 0.68% whereas the interassay CV was 0.06%, 0.96% and 0.28% respectively. The modified assay is highly sensitive being able to detect levels as low as 0.1 μmoles/l. In patients on maintenance haemodialysis CI measured by the original assay failed to detect any catalytic iron in almost all of these samples whereas by modified method it was measurable in all patients with a mean of 0.66 ± 0.10 μmoles/l. Normal values for catalytic iron in subjects having no comorbidities measured by modified method is 0.11 ± 0.06 μmoles/l.ConclusionsThe modified assay is reproducible and more sensitive than original assay and has been validated in several clinical studies.

BackgroundIt is well established that high bilirubin concentrations can lead to erroneous creatinine results when measured by a Jaffe-based method. However, the effects of bilirubin on enzymatic methods appear less well-defined. The Roche Cobas 8000 enzymatic creatinine (CREP2) has an unconjugated bilirubin icterus limit of 20 mg/dL, equivalent to a bilirubin concentration of 342 µmol/L. Many hepatology patients have bilirubin levels much higher than this limit, and laboratories are unable to release creatinine results on these complex patients. This is particularly challenging for patient management, as creatinine is a key test and is a prerequisite for many procedures, imaging studies and treatments.MethodsTwo spiking studies were carried out, the first to define the interference effect of bilirubin on enzymatic creatinine measurement, and the second to see if this interference could be mitigated via dilution. Serum samples (n = 50) were spiked with a concentrated bilirubin solution. Indices, bilirubin and creatinine were measured using the Roche Cobas 8000 c702 automated analyser according to manufacturer instructions.ResultsThe spiking study found a negative linear relationship and as bilirubin concentrations increased, the measured creatinine concentration decreased (R² = 0.7828, y = -0.0597x + 15.603). Samples with a bilirubin concentration over 246 µmol/L demonstrated an average 1.48% drop in creatinine concentration per 25 µmol/L increase in bilirubin.ConclusionsA service improvement was applied where creatinine results can be released on samples with a bilirubin concentration up to 550 µmol/L, with an appropriate comment, upon request by the clinician.

IntroductionAnalytical quality is a crucial prerequisite for best practice in medical laboratory. Six-Sigma Methodology (SM) is a quality measurement tool used to evaluate laboratory performance. This study aims to assess the analytical phase baseline performance using SM and compare results using TEa of CLIA 1988 and CLIA 2024.Materials and methodsCoefficient of variation and bias were determined for 14 analytes. The sigma level for each parameter was calculated using total allowable error (TEa) for CLIA 1988 and CLIA 2024. The quality goal index ratio was calculated for analytes with Sigma less than 3. Normalized method decision Charts were plotted for level 1 and 2 Bio-Rad internal quality control for both CLIA 1988 and 2024.ResultsUsing CLIA TEa 1988, HDL-C, triglycerides & uric acid for level 1 and ALT, AST, HDL-C, calcium, triglycerides & uric acid for level 2 had six Sigma world class performance, meanwhile, only BUN for level 1 and 2 performed less than 3. Using CLIA TEa 2024, HDL-C, GGT, and triglycerides for level 1 and ALT, AST, calcium, GGT, and triglycerides for level 2 had world class quality performance. Meanwhile, creatinine, glucose, BUN for level 1 and BUN and creatinine for level 2 performed less than 3.ConclusionEvaluation of baseline analytical performance using SM revealed lower sigma values with stringent CLIA TEa 2024 versus tolerant CLIA TEa 1988. Improvement in the methodology of analytes with poor performance on some assay platforms with stringent quality control regimes is recommended.

BackgroundA critical pre-analytical phase of newborn screening (NBS) testing involves the drying of blood applied to the blood collection devices to form the dried blood spots (DBS). Guidance states that blood applied should be air-dried for a minimum of 3 h. A recent survey highlighted that a number of DBS specimens routinely received into laboratories have a 'crinkled' appearance and that DBS specimens collected in a hospital setting are transported to the laboratory in sealed plastic bags. To date no scientific studies have evaluated aspects of blood drying on DBS NBS analyte concentrations.MethodsWe undertook experiments to recreate 'crinkled' DBS specimens in the laboratory and assess the impact on analyte concentrations. We also assessed the impact of storing collection devices following blood application in hermetically sealed plastic bags to impede the drying process. Experiments were performed using whole blood enriched with thyroid stimulating hormone, immunoreactive trypsinogen, phenylalanine, tyrosine, leucine, methionine, octanoyl-carnitine, decanoyl-carnitine, isovaleryl-carnitine and glutaryl-carnitine to pathophysiological concentrations.Results'Crinkled' DBS specimens produced significantly lower results (mean -15.5%, range -25.1 to -4.7%) for all analytes measured versus air-dried DBS specimens (P < .05). Analyte concentrations obtained from DBS specimens following storage in plastic bags before drying were significantly lower (mean -41.6%, range -60.0 to -27.6%) for all analytes measured (P < .05) versus air-dried DBS specimens.ConclusionResults from this study demonstrate that all DBS specimens with a crinkled appearance and those received in plastic specimen bags should be rejected and a repeat specimen collected to prevent erroneous screening results.

BackgroundMeasurement of urine free metadrenalines offers potential diagnostic and practical advantages over urinary fractionated metadrenalines in detection of phaeochromocytoma and paraganglioma, including sample collection without acid preservative. Here, we evaluate stability with and without sample acidification as well as pH implications for analysis by solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry.MethodsSpot urine samples were adjusted to pH 3 or unacidified on day of collection and stored at room temperature, 4°C or -20°C, for up to 28 days to assess changes in free metadrenaline concentrations over time. Extraction of unacidified versus acidified urine was examined by comparing peak areas and measuring concentrations present in sample eluents according to two SPE methodologies.ResultsFree metadrenalines remained stable in urine with or without acidification for up to 28 days, with mean reduction in concentrations of <10% for all storage conditions. Measured concentrations progressively increased without acidification at room temperature at low concentrations but remained constant when spiked with pathological concentrations. Peak areas were up to 97-fold lower in acidified than unacidified samples when extracted using weak cation exchange (WCX). On average 64% of analyte eluted in the flowthrough in acidified samples relative to 1.5% without acidification. By contrast, over 99% was retained in the extract using polar extraction at either pH.ConclusionUrine free metadrenalines remain stable at room temperature for up to 28 days and are more efficiently extracted without use of acid preservative if using WCX methodology.

BackgroundThe Japanese Red Cross Society measures levels of glycated albumin (GA), an indicator of mean blood glucose levels, in blood obtained from all donors.MethodsChanges in mean GA levels and the percentage of cases of prediabetes from 2009 to 2018 were investigated in approximately 4.2 million, healthy, first-time blood donors aged 16-64 years, and the seasonal characteristics of GA and the association of the GA level with body mass index (BMI) were clarified.ResultsMean GA levels decreased over the decade, with a decrease of 0.42-0.77% in male and 0.39-0.49% in female donors in the groups categorised by age. The percentage of prediabetes cases also decreased over the decade, with the largest decrease in those in their 60s. GA levels were higher in the warm season than in the cold season. In 2018, the seasonal difference in the GA level was 0.48% (95% confidence interval [CI] 0.45-0.50%) for male and 0.45% (95% CI 0.41-0.48%) for female donors. GA had a linear negative correlation with BMI in the younger generation. A trend of increasing GA with BMI was noted in those in their 30s and older.ConclusionsMean GA levels and the percentage of prediabetic cases have decreased, possibly resulting from public health promotion efforts and early diagnosis of diabetes mellitus. The present data on GA seasonal variation, showing higher levels in the warm season, and the association between BMI and GA may be useful for clinical practice.

Background: Thalassemias are inherited disorders caused by reduced production of structurally normal haemoglobin chains. Haemoglobin A2 (HbA2) constitutes an important parameter in the diagnostic evaluation of thalassaemias. Insight into the factors that modulate HbA2 levels is critical for correct interpretation of laboratory results in cases where thalassaemia is suspected. Methods: A retrospective study was conducted on patients who underwent haemoglobin analysis by high-performance liquid chromatography (HPLC) at Amsterdam UMC. Patients with elevated haemoglobin A1c (HbA1c) levels due to chronic hyperglycaemia were compared with controls, an iron deficiency cohort, and α-thalassemia cohorts. Results: Patients with strongly elevated HbA1c levels (110-180 mmol/mol) showed significantly reduced HbA2 levels compared with controls (2.0% vs. 2.4%, P<0.0001). This reduction in HbA2 fraction was not observed when HbA2 was expressed relative to non-glycated HbA instead of all haemoglobin fractions. Red cell indices (MCH, MCV) and haemoglobin concentrations remained unaffected. The degree of HbA2 reduction in patients with high HbA1c was comparable to that observed in iron deficiency and α-thalassemia. Conclusions: Elevated HbA1c levels due to chronic hyperglycaemia lower measured HbA2 fractions, confounding the diagnostic evaluation of thalassaemias. Laboratories should consider HbA1c status when interpreting HbA2 results in patients with poorly controlled diabetes. Expressing HbA2 relative to non-glycated HbA may improve diagnostic accuracy in such cases.

Proprotein Convertase Subtilisin-Kexin type 9 (PCSK9) is a key regulator of lipid metabolism, binding to the low-density lipoprotein receptor (LDLR) on the cell surface and preventing its recycling, thereby reducing clearance of LDL cholesterol (LDLc) from the circulation. For this reason, it constitutes an alternative therapeutic target for the control of hypercholesterolaemia, with the development of monoclonal antibodies against PCSK9 occurring within 12 years of the protein's discovery. Recent research has also suggested an inflammatory role played by PCSK9, with elevated plasma levels identified in critical illnesses such as sepsis and Acute Respiratory Distress Syndrome, where PCSK9 is thought to reduce bacterial endotoxin clearance and may exacerbate inflammation. Further work is required in order to clarify the exact role played by PCSK9 in extra-hepatic tissues, and the potential benefits of its pharmacological inhibition.