Rousseau Gama

Vitamin D: a negative acute phase reactant.

Objective We evaluated the effect of the systemic inflammatory response (SIR), as provoked by elective orthopaedic surgery, on serum vitamin D [25-(OH)D]. Methods Serum 25-(OH)D, serum vitamin D binding protein (VDBP) and urinary VDBP were measured in 30 patients before and 48-hours after knee or hip arthroplasty. C-reactive protein (CRP) was measured to assess the SIR. Results The mean (SD) CRP increased following surgery [5.0 (5.5) vs 116.0 (81.2) mg/L; P<0.0001] as did urine VDBP/Creatinine ratio [8 (9) vs 20 (25) pg/mmol; p=0.0004]. Serum 25-(OH)D [56.2 (30.3) vs 46.0 (27.6) nmol/L; p = 0.0006] and serum VDBP [334 (43) vs 298 (37) mg/L]; P<0.0001] decreased. Conclusions Serum 25-(OH)D is a negative acute phase reactant, which has implications for acute and chronic inflammatory diseases. Serum 25-(OH)D is an unreliable biomarker of vitamin D status after acute inflammatory insult. Hypovitaminosis D may be the consequence rather than cause of chronic inflammatory diseases.

Iron overload in the Asian community

Hereditary hemochromatosis is an iron overload disorder that can lead to the impairment of multiple organs and is caused by mutations in one or more different genes. Type 1 hemochromatosis is the most common form of the disease and results from mutations in the HFE gene. Juvenile hemochromatosis (JH) is the most severe form, usually caused by mutations in hemojuvelin (HJV) or hepcidin (HAMP). The autosomal dominant form of the disease, type 4, is due to mutations in the SLC40A1 gene, which encodes for ferroportin (FPN). Hereditary hemochromatosis is commonly found in populations of European origin. By contrast, hemochromatosis in Asia is rare and less well understood and can be masked by the presence of iron deficiency and secondary iron overload from thalassemia. Here, we provide a comprehensive report of hemochromatosis in a group of patients of Asian origin. We have identified novel mutations in HJV, HAMP, and SLC40A1 in countries not normally associated with hereditary hemochromatosis (Pakistan, Bangladesh, Sri Lanka, and Thailand). Our family studies show a high degree of consanguinity, highlighting the increased risk of iron overload in many countries of the developing world and in countries in which there are large immigrant populations from these regions.

Between-assay variability of faecal calprotectin enzyme-linked immunosorbent assay kits

Background Faecal calprotectin (f-Cp), a marker of intestinal inflammation, can be used to distinguish between functional and organic bowel disease. F-Cp, following extraction, is commonly quantified using enzyme-linked immunosorbent assays (ELISAs) but there are no data comparing the different f-Cp assays or sample extraction devices. We, therefore, evaluated and compared the performance of the Immunodiagnostik, Bühlmann and Eurospital f-Cp ELISA assays as well as the Roche, Immunodiagnostik and ScheBo Biotech commercial faecal extraction devices. We also briefly report results from a pilot f-Cp external quality assurance (EQA) scheme. Methods Imprecision, linearity, recovery, drift and limit of quantitation of the f-Cp assays were evaluated and between-assay variability assessed. The three commercial sample extraction devices were compared with the manual weighing method. Four faecal samples were distributed as part of a pilot EQA scheme to 15 laboratories using quantitative ELISA f-Cp assays. Results The three f-Cp assays demonstrated adequate intra-/interbatch imprecision, linearity and recovery. The crosscomparison study and EQA data demonstrated that, for the same sample, the Bühlmann assay reports up to 3.8 times higher f-Cp concentrations than the Immunodiagnostik and Eurospital assays. On average, the commercial extraction devices led to a 7.8-28.1% under-recovery of f-Cp in comparison to the manual weighing method. Conclusions Laboratories should be aware of the lack of the assay standardization, as demonstrated by the between-assay variability. A comparison between f-Cp concentrations reported by these assays and clinical markers of disease severity is required in order to determine their diagnostic accuracy. The EQA scheme represents the first available programme for f-Cp.

Spurious hyperkalaemia due to EDTA contamination: common and not always easy to identify

Background To study the detection and prevalence of spurious hyperkalaemia due to potassium ethylenediaminetetra-acetic acid (kEDTA) contamination. Methods In a one-month prospective study, serum EDTA, zinc, calcium, magnesium concentrations and alkaline phosphatase activity were measured in samples with serum potassium ≥6.0 mmol/L. Results Twenty-eight out of 117 hyperkalaemic samples were contaminated with EDTA. Only serum zinc values below the reference range had 100% sensitivity for indicating EDTA contamination, but even at an optimal specificity of 89% at least 12 potentially genuine hyperkalaemic samples would be rejected. Conclusion Spurious hyperkalaemia due to kEDTA contamination is common. Gross kEDTA contamination is obvious by marked unexpected hyperkalaemia, hypocalcaemia, hypomagnesaemia and hypozincaemia. Spurious hyperkalaemia due to low concentrations of kEDTA contamination can only be confidently detected by measurement of serum EDTA.

EDTA sample contamination is common and often undetected, putting patients at unnecessary risk of harm

Background:  Potassium ethylenediaminetetraacetic acid (EDTA) is a sample tube anticoagulant used for many laboratory analyses. Gross potassium EDTA contamination of blood samples is easily recognised by marked hyperkalaemia and hypocalcaemia. However, subtle contamination is a relatively common, often unrecognised erroneous cause of spurious hyperkalaemia. Potassium EDTA contamination may also cause hypomagnesaemia and hypozincaemia. There are, however, no data on the prevalence of EDTA contamination as a cause of hypocalcaemia, hypomagnesaemia and hypozincaemia.

Glycaemia‐independent ethnic differences in HbA1c in subjects with impaired glucose tolerance

Aim  To study the ethnic differences in HbA1c between Whites and South Asians with impaired glucose tolerance.

Diurnal variation in lipoprotein lipase activity

Background: We investigated whether variations in lipoprotein lipase activity, a key post-prandial enzyme involved in the removal of circulating dietary triglycerides, could contribute to the previously described nocturnal lipid intolerance. Methods: We studied lipoprotein lipase activity in 12 healthy volunteers (five women, seven men) at 11.30 h and 23.30 h on two separate occasions. Subjects consumed a high-fat mixed meal at 07.30 h for the morning study or 19.30 h for the evening study. Then, after a 4-h fast, subjects were given an intravenous bolus of 7500 U heparin. Blood samples were collected before and 15 min after heparin administration for measurement of lipoprotein lipase, hepatic lipase, triglycerides and non-esterified fatty acids concentrations. Results: Post-prandial post-heparin lipoprotein lipase activity was greater in the morning than in the evening (16.5±1.4 versus 14.4±1.0 µmol oleate/mL/h; P<0.05). Post-prandial post-heparin hepatic lipase activity was also greater in the morning than in the evening (8.7±1.5 versus 8.1±1.6 µmol oleate/mL/h; P=0.002). There were no other significant diurnal differences. Conclusion: We report a diurnal variation in post-prandial lipoprotein lipase activity. This is consistent with the notion that decreased nocturnal insulin sensitivity extends to insulins actions on lipoprotein lipase and provides a possible explanation for nocturnal lipid intolerance.

Ethnic differences in total and HDL cholesterol concentrations: Caucasians compared with predominantly Punjabi Sikh Indo-Asians

Background In comparison with Caucasians, Indo-Asians resident in the UK have similar total cholesterol but lower HDL cholesterol (HDLC) concentrations. It is however possible that cardiovascular risk factors may vary between culturally different Indo-Asians. Methods We present data on 223 Indo-Asians (129 men, 94 women) and 787 Caucasians (421 men, 366 women) in whom a laboratory-based coronary heart disease (CHD) risk score calculation had been requested. Results Total cholesterol concentrations were similar in Indo-Asians and Caucasians. HDLC concentrations were higher (P< 0·001) in Caucasians [1·4 (1·3–1·4) mmol/L; median (95% confidence intervals)] than in Indo-Asians [1·2 (1·2–1·3) mmol/L]. Indo-Asian women [1·2 (1·2–1·3) mmol/L], Indo-Asian men [1·2 (1·2–1·3) mmol/L] and Caucasian men [1·2 (1·2–1·3) mmol/L] had similar HDLC concentrations but these were all lower (P< 0·001) than those in Caucasian women [1·4 (1·3–1·4) mmol/L]. Conclusion We confirm low HDLC concentrations in Indo-Asians, but propose that this is solely due to low HDLC concentrations in Indo-Asian women. Since Indo-Asians in Wolverhampton are predominantly Punjabi Sikhs, we suggest that the difference between this study and previous reports may be due to heterogeneity of CHD risk factors within culturally diverse Indo-Asians.

Effect of order of draw of blood samples during phlebotomy on routine biochemistry results

Aim To investigate whether incorrect order of draw of blood samples during phlebotomy causes in vitro potassium ethylenediaminetetraacetic acid EDTA (kEDTA) contamination of blood samples. Methods Serum kEDTA, potassium, calcium, magnesium, alkaline phosphatase, zinc and iron concentrations were measured in blood samples drawn before and after collecting blood into kEDTA containing sample tubes by an experienced phlebotomist using the Sarstedt Safety Monovette system. Results EDTA was undetectable in all samples. The concentrations of other analytes were similar in blood samples drawn before and after collection of the EDTA blood sample. Conclusion Order of draw of blood samples using the Sarstedt Safety Monovette system has no effect on serum biochemistry results, when samples are taken by an experienced phlebotomist.

Effect of low serum total protein on sodium and potassium measurement by ion-selective electrodes in critically ill patients

Abstract Hypoproteinaemia may lead to spuriously high electrolyte values using indirect ion-selective electrodes (ISE) compared to direct ISEs. This study evaluates the impact on electrolyte status assessment of direct compared to indirect ISE sodium and potassium measurements in samples from critically ill patients who have a high prevalence of hypoproteinaemia. Serum sodium and potassium measurements were compared using indirect and direct ISE in 190 samples received from critical care units over a three-week period. Serum sodium and potassium measurements were higher (P<0.0001) using indirect ISE (140.0±5.0 and 4.5±0.6, respectively) compared to direct ISE (136.5±5.2 and 4.5±0.6, respectively). The calculated difference between indirect and direct ISE values for sodium increased as total protein concentration decreased (Y=7.2–0.07X, 95% CI slope –0.1 to –0.05, P<0.0001, r2=0.14). Hypoproteinaemia was present in 85% of samples. Indirect ISE, compared to direct ISE, misclassified 28% of samples as pseudonormonatraemia (19%), pseudohypernatraemia (8%), pseudonormokalaemia (0.8%) and pseudohyperkalaemia (0.4%). Hypoproteinaemia is common in critically ill patients and this may lead to spuriously high indirect ISE electrolyte measurements, resulting in significant misclassification of electrolyte (particularly sodium) status. In such patients, direct ISE (as employed in point-of-care testing) offers more accurate and consistent electrolyte results than does indirect ISE (commonly used in major laboratory analysers).