Troponin release after exertional vasovagal syncope

Troponin release following exertional vasovagal syncope has not previously been reported. A young man was investigated after being admitted twice with exertional syncope, each time followed by a 10-fold spike in troponin I over 24 h. Treadmill exercise tests reproduced his symptoms and demonstrated a vasovagal mechanism. During recovery, despite lying supine, he remained hypotensive for 5 min, with profound bradycardia and ST segment depression. We suspected that intense cardiovagal neural activity may have caused the troponin leak.

Point-of-care testing (POCT) and evidence-based laboratory medicine (EBLM) - does it leverage any advantage in clinical decision making?

Point-of-care testing (POCT) is the analysis of patient specimens outside the clinical laboratory, near or at the site of patient care, usually performed by clinical staff without laboratory training, although it also encompasses patient self-monitoring. It is able to provide a rapid result near the patient and which can be acted upon immediately. The key driver is the concept that clinical decision making may be delayed when samples are sent to the clinical laboratory. Balanced against this are considerations of increased costs for purchase and maintenance of equipment, staff training, connectivity to the laboratory information system (LIS), quality control (QC) and external quality assurance (EQA) procedures, all required for accreditation under ISO 22870. The justification for POCT depends upon being able to demonstrate that a more timely result (shorter turnaround times (TATs)) is able to leverage a clinically important advantage in decision making compared with the central laboratory (CL). In the four decades since POCT was adapted for the self-monitoring of blood glucose levels by subjects with diabetes, numerous new POCT methodologies have become available, enabling the clinician to receive results and initiate treatment more rapidly. However, these instruments are often operated by staff not trained in laboratory medicine and hence are prone to errors in the analytical phase (as opposed to laboratory testing where the analytical phase has the least errors). In some environments, particularly remote rural settings, the CL may be at a considerable distance and timely availability of cardiac troponins and other analytes can triage referrals to the main centers, thus avoiding expensive unnecessary patient transportation costs. However, in the Emergency Department, availability of more rapid results with POCT does not always translate into shorter stays due to other barriers to implementation of care. In this review, we apply the principles of evidence-based laboratory medicine (EBLM) looking for high quality systematic reviews and meta-analyses, ideally underpinned by randomized controlled trials (RCTs), looking for evidence of whether POCT confers any advantage in clinical decision making in different scenarios.

Fluorosis and periostitis deformans as complications of prolonged voriconazole treatment

We describe a case of development of painful periostitis deformans in a 39-year-old woman who was receiving long-term voriconazole treatment for Aspergillus infection as a complication of orthotopic liver transplant. Measurement of fluoride levels strongly supports fluorosis to be the mechanism of the voriconazole-induced periostitis deformans and supports the concept that such measurements might be of use in predicting this complication of long-term voriconazole treatment.

Validation of high-sensitivity troponin I in a 2-hour diagnostic strategy to assess 30-day outcomes in emergency department patients with possible acute coronary syndrome

OBJECTIVES

The study objective was to validate a new high-sensitivity troponin I (hs-TnI) assay in a clinical protocol for assessing patients who present to the emergency department with chest pain.

BACKGROUND

Protocols using sensitive troponin assays can accelerate the rule out of acute myocardial infarction in patients with low-risk (suspected) acute coronary syndrome (ACS).

METHODS

This study evaluated 2 prospective cohorts of patients in the emergency department with ACS in an accelerated diagnostic pathway integrating 0- and 2-h hs-TnI results, Thrombolysis In Myocardial Infarction (TIMI) risk scores, and electrocardiography. Strategies to identify low-risk patients incorporated TIMI risk scores= 0 or ≤ 1. The primary endpoint was a major adverse cardiac event (MACE) within 30 days.

RESULTS

In the primary cohort, 1,635 patients were recruited and had 30-day follow-up. A total of 247 patients (15.1%) had a MACE. The finding of no ischemic electrocardiogram and hs-TnI ≤ 26.2 ng/l with the TIMI = 0 and TIMI ≤ 1 pathways, respectively, classified 19.6% (n = 320) and 41.5% (n = 678) of these patients as low risk; 0% (n = 0) and 0.8% (n = 2) had a MACE, respectively. In the secondary cohort, 909 patients were recruited. A total of 156 patients (17.2%) had a MACE. The TIMI = 0 and TIMI ≤ 1 pathways classified 25.3% (n = 230) and 38.6% (n = 351), respectively, of these patients as low risk; 0% (n = 0) and 0.8% (n = 1) had a MACE, respectively. Sensitivity, specificity, and negative predictive value for TIMI = 0 in the primary cohort were 100% (95% confidence interval [CI]: 98.5% to 100%), 23.1% (95% CI: 20.9% to 25.3%), and 100% (95% CI: 98.8% to 100%), respectively. Sensitivity, specificity, and negative predictive value for TIMI ≤ 1 in the primary cohort were 99.2 (95% CI: 97.1 to 99.8), 48.7 (95% CI: 46.1 to 51.3), and 99.7 (95% CI: 98.9 to 99.9), respectively. Sensitivity, specificity, and negative value for TIMI ≤ 1 in the secondary cohort were 99.4% (95% CI: 96.5 to 100), 46.5% (95% CI: 42.9 to 50.1), and 99.7% (95% CI: 98.4 to 100), respectively.

CONCLUSIONS

An early-discharge strategy using an hs-TnI assay and TIMI score ≤ 1 had similar safety as previously reported, with the potential to decrease the observation periods and admissions for approximately 40% of patients with suspected ACS. (Advantageous Predictors of Acute Coronary Syndromes Evaluation [APACE] Study, NCT00470587; A 2 hr Accelerated Diagnostic Protocol to Assess patients with chest Pain symptoms using contemporary Troponins as the only biomarker [ADAPT]: a prospective observational validation study, ACTRN12611001069943).

Capillary glucose meter accuracy and sources of error in the ambulatory setting

Hand-held glucose meters are used throughout the health system by both patients with diabetes and also by health care practitioners. Glucose meter technology is constantly evolving. The current generation of meters and strips are quick to use and require a very small volume of blood. This review aims to describe meters currently available in New Zealand, for use in the ambulatory setting. It also aims to discuss the limits of meter performance and provide technical information that is relevant to the clinician, using locally available data. Commoner causes and consequences of end-user (patient and health professional) error are illustrated using clinical case examples. No meter offers definite advantages over other meters in all clinical situations, rather meters should be chosen because they fit the needs of individual patients and because the provider is able to offer appropriate educational and quality assurance backup to the meter user. A broad understanding of the advantages and disadvantages of the subsidised meter systems available in New Zealand will help the health practitioner decide when it is in the best interests of their patients to change or update meter technology.

Comparison of blood glucose meters in a New Zealand diabetes centre

Background

To assess the accuracy and precision of the Roche Performa and Medisense Optium Xceed (5 and 10 s reading) blood glucose meters.

Methods

Capillary blood samples were taken from 100 patients attending a diabetes centre and blood glucose measured on Roche Performa ( n = 4) and Medisense Optium Xceed 5 s ( n = 2) and 10 s reading ( n = 2) meters. Venous plasma glucose from samples taken simultaneously was measured by the laboratory hexokinase method as reference standard. Imprecision was determined on the meters by replicate analysis ( n = 20) of control solutions provided by the manufacturers and also patient venous whole-blood samples. Accuracy was assessed relative to the reference method by Bland–Altman plots, Passing and Bablok regression analysis, and both Clarke and consensus error grid analysis. Coefficients of variation (CVs) were calculated to determine imprecision.

Results

Bland–Altman and Passing–Bablok analysis confirmed significant systematic bias for all meters, with relative under-reading of higher glucose concentrations. Error grid analysis showed that <5% readings exceeded ±20% (or ±0.83 mmol/L for readings <4 mmol/L) deviation from the reference method (1%, 2% and 4% for the Roche, Optium 5 and 10 s meters, respectively). CVs were all <4% for the control solutions and <6% for patient samples.

Conclusions

Both Roche Performa and Medisense Optium glucose meters (5 and 10 s readings) perform satisfactorily and are acceptable for operational use.

Reporting of estimated glomerular filtration rate (eGFR) in New Zealand--what are the clinical laboratories doing?

INTRODUCTION

Recent guidelines recommend automatic reporting of estimated glomerular filtration rate (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) equation with every request for plasma creatinine in patients aged >18 years. We evaluated the uptake of this recommendation in New Zealand at 6 months after the time that these recommendations were made.

METHOD

A questionnaire was sent to all laboratories participating in the Royal Australasian College of Pathologists' General Chemistry Quality Assurance Program (RCPA QAP), asking whether laboratories routinely report eGFR, to what extent the specific recommendations have been followed and what feedback there had been from clinicians.

RESULTS

Over 69% of New Zealand laboratories report eGFR results with most requests for creatinine in patients aged >18 years. There are, however, significant deviations from the specific recommendations made.

CONCLUSIONS

The uptake of eGFR reporting in New Zealand is high. Areas of importance for refinement of eGFR reporting in New Zealand have also been identified. While there has been little feedback from clinicians on eGFR reporting, it is mostly positive.

Clinical indications for the investigation of porphyria: case examples and evolving laboratory approaches to its diagnosis in New Zealand

Patients with porphyria present in a diverse and unusual variety of ways and most clinicians will see only a few cases, if any, during their professional lives. Porphyria may present (1) with acute symptoms, which may be abdominal pain, neurological or psychiatric; (2) with skin rash or photosensitivity; or (3) with a putative family history. Screening for latent porphyria has been greatly facilitated by fluorescence emission scanning of plasma and by mutational analysis. Our reference laboratory has recently diagnosed several cases of the less common types of porphyria, which we postulate is due to the availability of these methods and to the changing population of New Zealand. Accurate screening and diagnosis of porphyria is important, as an acute porphyric attack is life-threatening and preventable. Retrospective diagnosis may be difficult.

Lead poisoning due to ingestion of Indian herbal remedies

A case of lead poisoning is presented. The patient had recently returned to New Zealand from the Indian subcontinent. This prompted a search that identified lead contamination of ingested medicinal products that had been prescribed in India. There have been several case reports of lead toxicity due to contamination of Indian herbal medicines, though none, to our knowledge, previously reported from New Zealand.

Measurement of thiopurine methyl transferase activity guides dose-initiation and prevents toxicity from azathioprine

AIM

To establish an assay service for thiopurine methyl transferase (TPMT) activity in order to facilitate dose initiation of thiopurine drug therapy and to define appropriate reference intervals and optimal cut-offs for the New Zealand population.

METHODS

407 patients underwent radio-enzymatic assay testing of TPMT activity prior to initiation of thiopurine drug therapy. Those with low activity also underwent genotyping for the abnormal *2, *3A, and *3C alleles.

RESULTS

A trimodal distribution of enzyme activity was seen consistent with the known polymorphic genetics for this enzyme. Three cases of homozygous deficiency were identified. The 'normal' range is 9.3 to 17.6 units/ml red blood cells (RBCs), but many heterozygotes have activity above the lower limit of his range. TPMT activity above 10.7 units/ml RBC identifies a normal genotype with 100% probability.

CONCLUSION

The normal range for TPMT has been established. The measurement of TPMT activity helps to guide dose initiation and may prevent toxicity from azathioprine.

Comparison of differing diagnostic criteria for diabetes: experience from a New Zealand community laboratory

AIMS

To compare rates of diabetes and impaired glucose tolerance in oral glucose tolerance tests (OGTTs) from a New Zealand community laboratory applying differing diagnostic criteria.

METHODS

Results from 455 non-pregnant subjects in 75 g oral glucose tolerance tests were reviewed with diabetes assigned according to 1985 WHO criteria (either fasting plasma glucose (FPG) > or =7.8 mmol/L or two-hour glucose > or =11.1 mmol/L), the American Diabetes Association (ADA) criteria (FPG > or =7.0 mmol/L alone), or revised WHO criteria (adopted by the Australasian Working Party) for OGTT (either FPG > or =7.0 mmol/L or 2-h value of > or =11.1 mmol/L). Impaired glucose tolerance (IGT) was assigned according to 1985 WHO criteria (FPG <7.8 mmol/L and 2-h glucose > or =7.8 mmol but <11.1 mmol/L), impaired fasting glucose (IFG) according to the ADA criteria (FPG of > or =6.1 but <7.0 mmol/L), or combination of IFG and IGT (revised WHO criteria).

RESULTS

The 1985 WHO criteria assigned 266 cases (58.5%) as normal glucose tolerance (NGT), 93 (20.4%) as IGT and 96 (21.1%) as diabetic. The ADA fasting criterion assigned 299 (65.7%) as NGT, 82 (18%) as IFG and 74 (16.2%) as diabetic. Only 55 (47.8%) cases identified as diabetic by either criterion met both. Using the combination of FPG > or =7.0 mmol/L or the 2-h glucose of > or =11.1 mmol/L (revised WHO criteria), 115 (25.3%) were assigned as diabetic, 102 (22.4%) as IFG or IGT, and 238 (52.3%) as NGT.

CONCLUSIONS

There is thus a 22.9% decrease in diabetes with the ADA fasting criterion, compared with the 1985 WHO criteria. With revised WHO criteria (as adopted by the Australasian Working Party), there is a 19.8% increase in diabetes and a 9.7% increase in those with IFG/IGT. These figures have resource implications for the management of diabetes in New Zealand.

Acutely raised corticotropin levels in Addison's disease are not associated with increased plasma arginine vasopressin and corticotropin-releasing factor concentrations in peripheral plasma

Using an intensive sampling protocol we have examined the associations of peripheral plasma arginine vasopressin (AVP) and CRF with nocturnal ACTH hypersecretion in patients with Addison's disease. Six subjects were studied during a phase of cortisol withdrawal (36 h) and after cortisol substitution, and the findings were compared to those in four normal control subjects. The pulse properties of ACTH hypersecretion at a 10-min sampling interval have also been examined in these settings, using Cluster analysis. In the period before cortisol replacement, the Addison's patients showed significantly greater ACTH peak maxima and peak increments than the control subjects [107 +/- 44 vs. 5.5 +/- 1.3 pmol/L (P = 0.009) and 57 +/- 23 pmol/L vs. 3.7 +/- 0.9 pmol/L (P < 0.05), respectively]. After cortisol replacement, a significant decrease in mean peak increment (57 +/- 24 vs. 15 +/- 5 pmol/L; P = 0.021) occurred. The mean interpulse intervals did not differ significantly between the Addison's and control subjects (59 +/- 5 vs. 59 +/- 4 min overall). Although not significant, the trend for the pulse interval to increase after oral cortisol (60 +/- 6 vs. 72 +/- 9 min) is probably a result of the extremely low levels of ACTH after oral cortisol administration, making peak detection difficult. Despite the ACTH hypersecretion in the Addison's subjects, plasma AVP levels were at no time different from those in the control subjects. Plasma CRF levels tended to be lower in the Addison's patients than in the control subjects. We conclude that in states of cortisol deficiency, such as Addison's disease, ACTH hypersecretion results from enhanced ACTH peak amplitude, without a change in the frequency of ACTH secretory pulses. The marked increase in plasma ACTH that follows acute cortisol deprivation is independent of detectable changes in peripheral plasma levels of CRF or AVP.