Inappropriate trace element testing in the Auckland region.

AIM: To understand recent changes in trace element test usage in the Auckland region of New Zealand. METHODS: Laboratory records of trace element tests between 2004 and 2008 were analysed. A questionnaire was sent to a frequent requestor group to elicit reasons for requesting trace element tests. RESULTS: The annual number of trace element test requests increased by 3.5-fold over the study period. The increase was largely due to a 2.8-fold increase in serum copper, a 3.8-fold increase in serum zinc, and a 3.4-fold increase in serum selenium tests. Most of the increase was accounted for by a small number of requestors, mainly general practitioners. An outlier group of 24 requestors was identified who were responsible for ordering 55% of serum copper, 61% of serum zinc, 63% of serum selenium and 66% of blood mercury tests in the last year of the study. Responses to the questionnaire suggest that among the outlier group the reasons for requesting serum zinc, copper and selenium tests are not evidence-based. CONCLUSION: The majority of trace element tests performed in the Auckland region appear to be non-evidence-based, and represent a significant wastage of public laboratory resources. This suggests that laboratories could achieve significant savings in expenditure by clearly defining appropriate indications for performing trace element tests.

Statistical methods for monitoring the relationship between the IFCC reference measurement procedure for hemoglobin A1c and the designated comparison methods in the United States, Japan, and Sweden.

BACKGROUND: The American Diabetes Association (ADA)/European Association for the Study of Diabetes (EASD)/International Diabetes Federation (IDF)/IFCC Consensus Statement on the worldwide standardization of HbA(1c) states that "... [HbA(1c)] results are to be reported world-wide in IFCC units ... and derived NGSP units ... , using the IFCC-NGSP master equation." METHODS: We describe statistical methods to evaluate and monitor the relationships as expressed in master equations (MEs) between the IFCC Reference Measurement procedure (IFCC-RM) and designated comparison methods (DCMs) [US National Glycohemoglobin Standardization Program (NGSP), Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC), and Mono-S in Sweden]. We applied these statistics, including uncertainty calculations, to 12 studies in which networks of reference laboratories participated, operating the IFCC-RM and DCMs. RESULTS: For NGSP and Mono-S, slope, intercept, and derived percentage HbA(1c) at the therapeutic target show compliance with the respective MEs in all 12 studies. For JDS/JSCC, a slight deviation is seen in slope and derived percentage HbA(1c) in 2 of the 12 studies. Using the MEs, the uncertainty in an assigned value increases from 0.42 mmol/mol HbA(1c) (IFCC-RM) to 0.47 (NGSP), 0.49 (JDS/JSCC), and 0.51 (Mono-S). CONCLUSIONS: We describe sound statistical methods for the investigation of relations between networks of reference laboratories. Application of these statistical methods to the relationship between the IFCC-RM and DCMs in the US, Japan, and Sweden shows that they are suitable for the purpose, and the results support the applicability of the ADA/EASD/IDF/IFCC Consensus Statement on HbA1c measurement.

[Aldosterone-to-renin ratio threshold for screening primary aldosteronism in Chinese hypertensive patients].

OBJECTIVE: In recent years, the assessment of the plasma aldosterone-to-renin ratio (ARR) has become a most effectively and commonly used method for screening primary aldosteronism from hypertensive patients. It is known that there is a large variance in ARR value between races and ARR is affected by many factors, such as drugs, posture and serum potassium etc. The objective of this study is to establish the threshold of ARR for screening primary aldosteronism in Chinese hypertensive patients. METHODS: A total of 110 hypertensive patients were recruited and divided into essential hypertension group (n=65) and adenoma/hyperplasia group (n=45) according to the adrenal contrast CT scan. Antihypertensive drugs which can affect ARR such as beta-blockers, dihydropyridine calcium channel blockers (CCBs), ACE inhibitors (ACEIs), angiotensin II receptor blockers (ARBs) and clonidine, were withdrawn for at least 2 weeks. Washout period for diuretics including spironolactone were 4 weeks. Non-dihydropyridine calcium channel blockers (slow released verapamil) and/or alpha-blocker (terazosin) are allowed for controlling blood pressure when needed. If the serum potassium value<3.6 mmol/L, an oral potassium supplement was prescribed. After keeping upright position for 2 hours, blood samples were drawn for PRA and PAC measurement between 9:00AM-10:00AM. RESULTS: ARR was 100.00+/-48.65 (14.19-285.16) pg/ml vs ngxml-1xh-1 in patients with essential hypertension and 699.33+/-213.33 (185.8-2150) pg/ml vs ngxml-1xh-1 in patients with adenoma/hyperplasia. ARR value was greater than 240 in 42 out of 45 patients (93.3%) with adenoma/hyperplasia and was less than 240 in 59 out of 65 (90.7%) patients with essential hypertension. We used ARR 240 as the cut-off threshold for screening primary aldosteronism in another 178 hypertensive patients and ARR was greater than 240 in all 15 patients with confirmed primary aldosteronism. CONCLUSION: It is suitable to use upright ARR 240 as a cut-off threshold for screening primary aldosteronism in Chinese hypertensive patients.