Clinical laboratory reference intervals in pediatrics: The CALIPER initiative

Objective and rationaleReference intervals provided on laboratory reports are essential for appropriate interpretation of test results, and can significantly impact clinical decision-making and the quality of patient care. Careful determination and/or validation of reference intervals by the laboratory for use in the patient population it serves are therefore important to ensure their proper utility. Unfortunately, critical gaps currently exist in accurate and up-to-date pediatric reference intervals for accurate interpretation of laboratory tests performed in children and adolescents. These critical gaps in the available pediatric laboratory reference intervals have the clear potential of contributing to erroneous diagnosis or misdiagnosis of many diseases of childhood and adolescence. Most of the available “normal” ranges for laboratory tests were determined over 2 decades ago on older instruments and technologies, and are no longer relevant considering the current testing technology used by clinical laboratories. It is thus critical and of utmost urgency that a more acceptable and comprehensive database be established.Discussion and conclusionIn the present review, we discuss the considerations and challenges faced when generating and validating reference intervals in accordance to the current guidelines published by the Clinical Laboratory Standards Institute (CLSI). We raise particular attention to the present-day deficiencies in available pediatric reference intervals, and highlight the special issues and unique difficulties that are additionally faced when establishing reference intervals in children. Finally, we highlight a recent Canadian initiative, the CALIPER project, whose mandate is to establish and maintain a database of comprehensive and up-to-date pediatric reference intervals to be eventually made available to all clinical laboratories worldwide.     

Challenges of implementing point-of-care testing (POCT) glucose meters in a pediatric acute care setting

OBJECTIVES: To investigate factors contributing to analytical bias in POCT glucose values generated by the NICU versus the core laboratory. METHODS: The LifeScan Flexx hospital system glucose meters (SureStep) were used in precision and comparison studies between the NICU and laboratory (ABL715 and Vitros 950). RESULTS: Analysis of 40 neonatal blood samples revealed a positive bias between the NICU glucose meters versus either the laboratory glucose meter or instrument (mean difference of 0.28 and 0.21 mmol/L, respectively). Linear regression analysis (R2 = 0.0584) of the difference in glucose results versus time elapsed between measurements indicated that the bias observed between the NICU and laboratory glucose meters was not due to in vitro glycolysis for samples transported on ice. Further analysis indicated that the bias appeared to be mostly operator driven, with different NICU operators exhibiting different mean biases. Increasing the amount of blood applied to the SureStep Pro test strip (e.g., 60 vs. 20 microL), led to higher values for glucose concentration for the same blood. Nearly 50% of all glucose values reported for the NICU were obtained by the SureStep Flexx glucose meters in a 3-month period following the introduction of POCT, yet the number of laboratory-reported glucose results for the same period increased by 21% as compared to the previous year. CONCLUSIONS: Operator error appears to be a source of bias present between the NICU and laboratory, and despite glucose meter utilization in the NICU, the number of glucose measurements by the central laboratory increased after POCT introduction.     

Cancer prevention: a new era beyond cyclooxygenase-2

The seminal epidemiological observation that nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and possibly other cancers has spurred novel approaches to cancer prevention. The known inhibitory effect of NSAIDs on the eicosanoid pathway prompted studies focusing on cyclooxygenase (COX) and its products. The increased prostaglandin E2 levels and the overexpression of COX-2 in colon and many other cancers provided the rationale for clinical trials with COX-2 inhibitors for cancer prevention or treatment. Their efficacy in the prevention of sporadic colon and other cancers remains unknown; one COX-2 inhibitor has been withdrawn because of side effects, and there are concerns about whether these effects are class-specific. There is evidence to suggest that COX-2 may not be the only or ideal eicosanoid pathway target for cancer prevention. Six sets of observations support this notion: the relatively late induction of COX-2 during carcinogenesis; the finding that NSAIDs may not require inhibition of COX-2 for their effect; the modest effect of coxibs in cancer prevention; that currently available coxibs have multiple non-COX-2 effects that may account for at least some of their efficacy; the possibility that concurrent inhibition of COX-2 in non-neoplastic cells may be harmful; and the possibility that COX-2 inhibition may modulate alternative eicosanoid pathways in a way that promotes carcinogenesis. Given the limitations of COX-2-specific inhibitors and the biological evidence mentioned above, we suggest that targets other than COX-2 should be pursued as alternative or complementary approaches to cancer prevention.     

New insights into how the intestine can regulate lipid homeostasis and impact vascular disease: frontiers for new pharmaceutical therapies to lower cardiovascular disease risk

In recent years, evidence has emerged that the intestine is a significant regulator of systemic cholesterol homeostasis and can contribute to raised plasma cholesterol concentration. In this review we provide a context for the role the intestine may have in cardiovascular disease during conditions of chronic disease (insulin resistance, obesity). In particular, we highlight the physiological role of the intestine in lipid absorption, identify novel elements in enterocyte molecular biology, review the concept that chylomicrons and their remnants contribute to atherogenesis during chronic disease, and address new principles of chylomicron overproduction during conditions of insulin resistance including the associated hormonal control of the intestine during these conditions. Finally, we raise the issue of a growing need for novel lipid-lowering pharmaceutical therapies that target intestinal lipid metabolism.     

Insulin sensitivity and secretion in children and adolescents with hypothalamic obesity following treatment for craniopharyngioma

Background Craniopharyngioma (CP), a tumour occurring in the hypothalamic–pituitary area, results in morbid obesity in 25–60% of affected children. It has been suggested that abnormalities of insulin secretion and/or insulin action due to hypothalamic injury may be associated with weight gain and the metabolic syndrome in this population. Aim To evaluate: (i) insulin secretion (IS) and insulin sensitivity (Si); (ii) features of the metabolic syndrome (MS) and (iii) factors involved in risk for diabetes and heart disease in obese youth treated for CP. Methods Obese subjects treated for CP were compared to BMI‐matched control subjects. All subjects underwent anthropometric, blood pressure, resting energy expenditure and body fat assessment. Cholesterol and inflammatory markers, oral glucose tolerance test (OGTT) and frequent sampling intravenous glucose tolerance test (FSIGT), with calculation of IS and Si, were performed. Results Fifteen CP subjects and 15 controls (C) were studied. There were no differences between CP and C for age, gender, BMI or pubertal status. MS was present in 10/15 CP and 3/15 C (P = 0·03), including impaired glucose tolerance (IGT) in 6/15 CP and 0/15 C (P = 0·02). Measures of IS, including first and second phase IS, and insulin area‐under‐the‐curve (AUC_ins) during OGTT, were significantly higher in CP. Si, measured by frequent sampled intravenous glucose tolerance test (Si‐FSIGT), was significantly lower in CP subjects (0·96 ± 0·34 vs. 1·67 ± 0·7; P = 0·01). AUC_ins was negatively correlated with Si‐FSIGT (r = ?0·62; P = 0·003). Conclusion Children with CP and hypothalamic obesity have more features of MS, increased IS and IGT prevalence and lower Si compared with BMI‐matched controls.     

Simvastatin,an HMG-CoA reductase inhibitor,induces the synthesis and secretion of apolipoprotein AI in HepG2 cells and primary hamster hepatocytes

Clinical studies have recently suggested that statin treatment may beneficially elevate plasma concentrations of high density lipoprotein (HDL)-cholesterol in patients with hyperlipidemia. Here, we have investigated the effect of a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase on the synthesis and secretion of apolipoprotein AI (apoAI) in two model systems, HepG2 cells and primary hamster hepatocytes. Cultured cells were incubated with different doses of simvastatin (0.1-10 microM) for a period of 18 h. A dose-dependent increase in synthesis and secretion of apoAI was observed in both cell types. There was a significant increase in the synthesis of apoAI in HepG2 cells (44.3+/-12.1%), and hamster hepatocytes (212+/-2%) after treatment with 10 microM of the statin. The increase in apoAI synthesis appeared to result in a higher level of apoAI secreted into the culture media in both cell types (49.2+/-7.8% in HepG2, 197+/-0.2% in hamster hepatocytes). ApoAI mRNA levels were also significantly increased in both cell types in response to statin treatment. Control experiments with transferrin confirmed specificity of the effect on apoAI secretion. Analysis of a density fraction containing HDL particles in culture media revealed an increase in HDL-associated apoAI of 94.3+/-2.1% in HepG2 cells and 27.0+/-0.03% in hamster hepatocytes following 10 microM simvastatin-treatment. Comparative studies of simvastatin and lovastatin indicated a differential ability to induce apoAI synthesis and secretion, with simvastatin having a more significant effect. Thus, acute statin treatment of cultured hepatocytes (transformed as well as primary) resulted in a significant upregulation of apoAI mRNA and apoAI synthesis, causing oversecretion of apoAI and HDL extracellularly. The stimulatory effect on apoAI synthesis and secretion may thus explain the clinical observation of an elevated plasma HDL-cholesterol level in hyperlipidemic patients treated with certain statins.