Performance of cardiac troponins within the HEART score in predicting major adverse cardiac events at the emergency department.

BACKGROUND: This study compared the performance of a single blood draw of high-sensitivity troponin T (hsTnT), high-sensitivity troponin I (hsTnI) and conventional troponin I (cTnI) within a modified HEART score for predicting 30-day MACE at Emergency Department (ED) presentation, and established local reference norms for all three assays by determining the cut-off point which yielded the highest sensitivity and negative predictive value for acute myocardial infarction and 30-day MACE. METHODS: This single-center prospective cohort study recruited chest pain patients at the ED, whose hsTnT, hsTnI and cTnI were taken on admission. Subjects were classified into low and non-low risk group according to their modified HEART score, with MACE as the primary endpoint. Receiver-operating characteristic (ROC) curves were generated, area under the curves (AUCs) were calculated; the performance characteristics were determined. RESULTS: The performance of modified HEART scores was comparable among the three assays for 30-day MACE (84.9-87.0% sensitivity, 95.6-96.0% NPV, 95%CI) and none of these had very high AUC and specificity (AUC 0.70-0.71, 53.7-56.7% specificity, 95% CI). The modified HEART score using a single blood draw of either hsTnT (3.9ng/L), hsTnI (0.9ng/L) or cTnI (0.0ng/L) at presentation yielded a sensitivity of 100% for 30-day MACE. CONCLUSION: The modified HEART score using a single blood draw of either hsTnT, hsTnI or cTnI was equally effective in risk-stratifying chest pain patients for safe discharge. The theoretical cut-off points yielding 100% sensitivity are potentially useful (when achieved) for safely discharging low risk patients with undifferentiated chest pain in the ED.

Commutable whole blood reference materials for hemoglobin A1c validated on multiple clinical analyzers.

Background The measurement of hemoglobin A1c (HbA1c) is important for diagnosing diabetes mellitus as well as assessing glycemic control in diabetic patients. Commutable whole blood certified reference materials (CRMs) are needed in the measurement of HbA1c for method validation and/or as quality controls. Methods We developed three levels of hemolyzed whole blood CRMs for HbA1c. The certified values were determined using liquid chromatography-isotope dilution tandem mass spectrometry method (LC-IDMS/MS) where two "signature" hexapeptides of HbA1c and hemoglobin A0 (HbA0) were used as the calibration standards. The concentrations of the hexapeptide solutions were determined by amino acid analysis by the LC-IDMS/MS method using amino acid CRMs as the calibration standards. The commutability study was conducted by measuring 25 patient specimens and the whole blood CRMs by both LC-IDMS/MS method and various routine methods using six different clinical analyzers. Results The certified values were determined to be 35.1±2.0, 50.3±1.9 and 65.8±2.6 mmol/mol, respectively. These CRMs showed good commutability on five of the six clinical analyzers but showed poor commutability on one of the clinical analyzers that used similar method as two other analyzers where good commutability was observed. Conclusions With certified target values based on metrological traceability and good commutability on most of the clinical analyzers, the developed whole blood CRMs can be used for method validation or as quality control materials in the measurement of HbA1c. The commutability study results also underscored the need of commutability testing of clinical CRMs using various clinical analyzers.

Small Incidental Pheochromocytoma Presenting With Normal or Borderline High 24-hour Urine Fractionated Metanephrines.

A 73-year-old man was found to have a 2-cm lipid-poor right adrenal incidentaloma on computed tomography imaging for hematuria. Twenty-four-hour urine metanephrine was 1.1-fold elevated, then normal on repeat measurement. Paired with the second urine collection, plasma metanephrine measured by liquid chromatography tandem mass spectrometry after a 30-minute supine rest was 3.3-fold elevated. Plasma normetanephrine was 1.2-fold elevated. The 24-hour urine catecholamines and normetanephrine, measured twice, were normal. He received low-dose phenoxybenzamine and underwent successful resection of right pheochromocytoma. Postoperatively, both plasma metanephrine and normetanephrine levels normalized, using an age-appropriate upper reference limit for plasma normetanephrine. Patients who harbor small lipid-poor adrenal incidentalomas have a relatively high risk (>5%) of having pheochromocytoma, indistinguishable from adenomas or carcinomas on computed tomography scan. In such cases when 24-hour urine fractionated metanephrines are normal, plasma free metanephrines measured by liquid chromatography tandem mass spectrometry under optimal sampling conditions that are 2-fold or more elevated confirm the diagnosis of pheochromocytoma. Preoperative alpha blockade followed by surgical resection is then appropriate, rather than continued monitoring with repeat urine measurements.

RNase2 is a possible trigger of acute-on-chronic inflammation leading to mRNA vaccine-associated cardiac complication.

BACKGROUND: Post-mRNA vaccination-associated cardiac complication is a rare but life-threatening adverse event. Its risk has been well balanced by the benefit of vaccination-induced protection against severe COVID-19. As the rate of severe COVID-19 has consequently declined, future booster vaccination to sustain immunity, especially against infection with new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, may encounter benefit-risk ratios that are less favorable than at the start of the COVID-19 vaccination campaign. Understanding the pathogenesis of rare but severe vaccine-associated adverse events to minimize its risk is thus urgent. METHODS: Here, we report a serendipitous finding of a case of cardiac complication following a third shot of COVID-19 mRNA vaccine. As this case was enrolled in a cohort study, pre-vaccination and pre-symptomatic blood samples were available for genomic and multiplex cytokine analyses. FINDINGS: These analyses revealed the presence of subclinical chronic inflammation, with an elevated expression of RNASE2 at pre-booster baseline as a possible trigger of an acute-on-chronic inflammation that resulted in the cardiac complication. RNASE2 encodes for the ribonuclease RNase2, which cleaves RNA at the 3' side of uridine, which may thus remove the only Toll-like receptor (TLR)-avoidance safety feature of current mRNA vaccines. CONCLUSIONS: These pre-booster and pre-symptomatic gene and cytokine expression data provide unique insights into the possible pathogenesis of vaccine-associated cardiac complication and suggest the incorporation of additional nucleoside modification for an added safety margin. FUNDING: This work was funded by the NMRC Open Fund-Large Collaborative Grant on Integrated Innovations on Infectious Diseases (OFLCG19May-0034).

Automation and productivity in the clinical laboratory: experience of a tertiary healthcare facility.

Clinical laboratories for in vitro diagnostics are facing pressure to preserve cost control while providing better services through new initiatives. Laboratory automation is a partial answer to this problem, having come a long way from the early days of clinical laboratory testing. The journey and implementation of automation in the Singapore General Hospital's Clinical Biochemistry Laboratory has allowed for sustained performance in the light of increasing workload and service commitments amid an evolving healthcare environment. Key to realising predicted outcomes is the optimisation of workflow processes, reduction of errors, and spatial placement of specimen reception and analytical areas. This paper gives an overview of our experience with automation in the clinical laboratory and its subsequent impact on service standards.

Effects of genetic immunization of Swiss outbred mice with human thyroid stimulating hormone receptor cDNA plasmids harboring gain-of-function mutations.

Animal models of Graves' disease have been generated in recent years with various vaccination protocols using wild-type TSH receptor. In this study, we report the findings of genetic immunization of Swiss outbred mice with three different mutated human TSH receptor plasmids, each containing one constitutive activating mutation located at the ectodomain (S281N), exoloop (I486F), and transmembrane segment (D633H) respectively. Although the overall rate of thyrotoxicosis in the mice was < 10%, anti-TSH receptor antibodies could be detected in many animals by flow cytometry, radioreceptor assay, and functional bioassays using recombinant human TSH receptor. Mice injected with plasmids harboring activated mutants (S281N and D633H) showed production of predominantly stimulating antibodies, whilst those treated with wild-type receptor plasmids generated mainly blocking sera. Most of these antibodies displaced radiolabeled bovine TSH, and their epitopes, independent of functional characteristics, were mapped to the first 271 amino acids of the TSH receptor. This supports recent findings that binding of stimulatory or blocking antibodies lie in close proximity within the leucine-rich repeat region.

Reference range of thyroid hormones in very low birth weight infants at the time of discharge.

AIM: There is little information regarding the reference range for thyroid hormones in preterm babies, especially those with very low birth weight (VLBW) of less than 1500 g. The objective of our study was to evaluate the relationship between thyroid hormone levels and postmenstrual age in a cohort of stable VLBW infants. METHOD: An observational cohort study of VLBW infants preparing for discharge from a high-dependency nursery in Singapore. The infants' free thyroxine (fT4) and thyrotropin (TSH) levels were assayed just before discharge and correlated with postmenstrual age, calculated as the sum of the duration of gestation at birth and chronological age in weeks. RESULTS: fT4 and TSH levels were sampled in 129 ex-VLBW babies at a mean postmenstrual age of 38.5 (±4.6) weeks. The babies were born at a mean±SD gestation of 28.9±2.4 weeks (median 29.0 weeks, range 24.0-34.5 weeks) with mean±SD birth weight of 1081±268 g (median 1090 g, range 490-1490 g). Linear regression analysis revealed negative and fair correlation between fT4 and postmenstrual age (r=-0.302). The mean±SD fT4 level was 16.8±3.2 pmol/L (median 16.8 pmol/L, range 8.5-28.9 pmol/L). However, there was only a very weak negative correlation between TSH levels and postmenstrual age, both with (r=-0.116) or without logarithmic transformation. The mean±SD TSH was 4.56±2.50 mIU/L (median 4.42 mIU/L, range 1.0-13.5 mIU/L). CONCLUSION: Our study shows a fair and inverse correlation of fT4 with postmenstrual age in a large cohort of growing ex-VLBW infants, in keeping with maturation of the hypothalamic-pituitary-thyroid axis. It suggests that fT4 levels in growing infants are best compared to postmenstrual age-specific norms instead of a single reference interval.

Thrombin-accelerated quick clotting serum tubes: an evaluation with 22 common biochemical analytes.

Clot activator serum tubes have significantly improved turnaround times for result reporting compared to plain tubes. With increasing workload and service performance expectations confronting clinical laboratories with high-volume testing and with particular emphasis on critical analytes, attention has focussed on preanalytical variables that can be improved. We carried out a field study on the test performance of BD vacutainer rapid serum tubes (RSTs) compared to current institutional issued BD vacutainer serum separator tubes (SSTs) in its test result comparability, clotting time, and stability on serum storage. Data from the study population (n = 160) of patients attending outpatient clinics and healthy subjects showed that results for renal, liver, lipids, cardiac, thyroid, and prostate biochemical markers were comparable between RSTs and SSTs. Clotting times of the RSTs were verified to be quick with a median time of 2.05 min. Analyte stability on serum storage at 4°C showed no statistically significant deterioration except for bicarbonate, electrolytes, and albumin over a period of 4 days. In conclusion, RSTs offered savings in the time required for the clotting process of serum specimens. This should translate to further trimming of the whole process from blood collection to result reporting without too much sacrifice on test accuracy and performance compared to the current widely used SSTs in most clinical laboratories.

Haemoglobin A1c: evaluation of a new HbA1c point-of-care analyser Bio-Rad in2it in comparison with the DCA 2000 and central laboratory analysers.

BACKGROUND: Point-of-care-testing (POCT) of haemoglobin Alc (HbA1c) is popular due to its fast turnaround of results in the outpatient setting. The aim of this project was to evaluate the performance of a new HbA1c POCT analyser, the Bio-Rad in2it, and compare it with the Siemens DCA 2000, Bio-Rad Variant II and Roche Tina-quant HbA1c Gen 2 assay on the cobas c501. METHODS: Imprecision of the four methods were compared by computing total imprecision from within-run and between-run data. A total of 80 samples were also compared and analysed by Deming regression and Altman-Bland difference test. RESULTS: Study of total imprecision of the in2it at HBA1c levels of 6.0% and 10.4% produced a coefficient of variation (%CV) of 3.8% and 3.7%, respectively. These results were more favourable as compared with the DCA 2000 but did not match the low imprecision of the central laboratory methods, the Bio-Rad Variant II and the Roche cobas c501. Comparison between the in2it and the central laboratory analysers, Bio-Rad variant II and cobas c501, revealed positive bias of 12% and 10%, respectively, supported by corresponding Deming regression equation slopes of +1.18 and +1.14. Comparison between the DCA 2000 and the central laboratory analysers revealed a bias that became increasingly positive with rising HbA1c concentrations with Deming regression analysis also revealing proportional and constant differences. CONCLUSIONS: The in2it is a suitable POCT analyser for HbA1c but its less than ideal precision performance and differences with the central laboratory analysers must be communicated to and noted by the users.