Plasma or serum 5-hydroxyindoleacetic acid can be used interchangeably in patients with neuroendocrine tumours

5-hydroxyindole acetic acid, a metabolite of serotonin, is used in the diagnosis and monitoring of patients with neuroendocrine tumours, in particular patients with small intestinal neuroendocrine tumours associated with the carcinoid syndrome. Analysis of 5-hydroxyindole acetic acid was commonly performed in urine, but blood-based assays are now becoming available. The objective of this study was to assess how 5-hydroxyindole acetic acid compares in plasma and serum as a biochemical marker of neuroendocrine tumours. Twenty-four-hour urine, plasma and serum samples were obtained from 80 patients with neuroendocrine tumours and 30 healthy volunteers. We developed a liquid chromatography tandem mass spectrometry assay for plasma and serum 5-hydroxyindole acetic acid. Comparison was made between them, and their cut-off was determined using a receiver-operating characteristic curve. A close correlation was shown between plasma and serum 5-hydroxyindole acetic acid. At a cut-off of 135 nmol/l, a sensitivity of 91.2% with a specificity of 61.9% was obtained for both compared to the urinary assay. A statistically significant agreement was shown when plasma and serum 5-hydroxyindole acetic acid were compared with the currently used urine assay in patients with neuroendocrine tumours; κ = 0.675 (95% CI 0.49 to 0.86), p < 0.001 and healthy volunteers; 0.967 (95% CI 0.828 to 0.999), p = <0.001. In conclusion, 5-hydroxyindole acetic acid in plasma and serum were comparable, hence either sample type can be used interchangeably.

The role of 5-hydroxyindoleacetic acid in neuroendocrine tumors: the journey so far

5-Hydroxyindole acetic acid (5-HIAA) is a surrogate marker for serotonin measurement and one of the first biochemical markers used in neuroendocrine tumors. In this review, we give a brief history of 5-HIAA and its precursor serotonin. We discuss its clinical utility and diagnostic performance in small intestinal neuroendocrine tumor and describe the challenges encountered during its analysis, historically performed in urine. The introduction of blood-based assays will help overcome some of the issues associated with its measurement in urine. The diagnostic performance of serum and plasma 5-HIAA has been shown to be comparable to that of urine 5-HIAA. Thus, analysis in either serum or plasma will provide a practical and convenient alternative to urine.

Vitamin K and other markers of micronutrient status in morbidly obese patients before bariatric surgery

BACKGROUND

Micronutrient deficiencies occur in morbidly obese patients. The aim of this study was to assess vitamin deficiencies prior to bariatric surgery including vitamin K about which there is little data in this population.

METHODS

A prospective assessment of 118 consecutive patients was performed. Clinical allied with haematological and biochemical variables were measured. Micronutrients measured included vitamins K1 , PIVKA-II (protein-induced in vitamin K absence factor II), vitamin D, vitamin B12 (holotranscobalamin), iron, transferrin and folate.

RESULTS

Patients were aged 49 ± 11 [mean (SD, standard deviation)] years, body mass index (BMI) 50 ± 8 kg/m(2), 66% female and 78% Caucasian. Hypertension was present in 47% and type 2 diabetes in 32%. Vitamin D supplements had been prescribed in 8%. Micronutrient insufficiencies were found for vitamin K (40%), vitamin D (92%) and vitamin B12 (25%), and also iron (44%) and folate (18%). Normocalcaemic vitamin D insufficiency with secondary hyperparathyroidism was present in 18%. Iron and transferrin levels were associated with age, sex and estimated glomerular filtration rate. Vitamin K levels were associated with age, and inversely with BMI and diabetes mellitus; and PIVKA-II with smoking, triglycerides and liver function markers. Vitamin D levels were associated with statin use and prescription of supplements and inversely with BMI. Vitamin B12 levels were associated with ethnicity and HbA1c.

CONCLUSION

Micronutrient status shows differing relationships with age, gender and BMI. Vitamin K insufficiency was present in 40% and not related to deficiencies in other vitamins or micronutrients. Vitamin D and vitamin K supplementation should be considered prebariatric surgery in patients with diabetes or severe insulin resistance.

Dyslipidaemia: what's around the corner?

Hyperlipidaemia is a major risk factor for the development of atherosclerosis and cardiovascular disease. Statins are the mainstay of therapy and new guidelines focus on the use of these agents without specific targets for low-density lipoprotein (LDL)-cholesterol or non high-density lipoprotein (HDL)-cholesterol. However, patients remain at risk of cardiovascular disease despite statin therapy so new drugs are required. This article reviews therapies in development to further lower LDL-cholesterol (Proprotein convertase subtilisin/kexin-9 (PCSK-9) inhibitors), raise HDL-holesterol (cholesterol ester transfer protein inhibitors (CETPIs)) and reduce triglycerides (novel peroxisome proliferator-activated receptor (PPAR)-agonists and omega-3 fatty acid preparations). Specialised therapies are in development for treatment of orphan disoders such as homozygous familial hypercholesterolaemia (lomitapide) or familial chylomicroaemia (alipogene tiparvovec). These novel lipid-lowering agents are likely to find uses in treating patients at the highest cardiovascular risk.

An association between post-meal bile acid response and bone resorption in normal subjects

Background

The mechanism surrounding bone suppression after a meal may involve several mediators, but is yet to be clarified. Bile acids (BA) function as signalling molecules in response to feeding, and may be directly involved in bone suppression acutely after a meal. The aim of this study was to test the hypothesis that BA are involved in the acute bone suppression observed after a meal.

Methods

A prospective study in which samples collected from volunteers fed a 400 Kcal test meal after an overnight fast were analysed for parathyroid hormone (PTH), BA, and carboxyterminal of type 1 collagen telopeptide (CTX). The study was carried out in 10 healthy male volunteers. Ethical approval was obtained from the Local Research and Ethics Committee at King's College Hospital.

Results

Total BA, glycine conjugated bile acids (GCBA), PTH and CTX showed a response to meal ingestion. There was a negative correlation between percentage change in PTH and CTX ( R2 = −0.82, P = 0.004), and between PTH and GCBA ( R2 = −0.39, P = 0.005).

Conclusion

This study demonstrated an association between GCBA and PTH suppression after a meal. The drop in PTH concentration after a meal may be responsible for the suppression of bone resorption as observed by the decrease in CTX concentration.

Lipid-lowering agents

The role of lipid lowering in reducing the risk of mortality and morbidity from cardiovascular disease (CVD) is well established. Treatment particularly aimed at decreasing low-density lipoprotein cholesterol (LDL-C) is effective in reducing the risk of death from coronary heart disease and stroke. Statins form the cornerstone of treatment. However, in some individuals with a high risk of CVD who are unable to achieve their target LDL-C due to either intolerance or lack of efficacy, there is the need for alternative therapies. This review provides an overview of the different classes of currently available lipid-lowering medications including statins, fibrates, bile acid sequestrants (resins), and omega-3 fatty acids. Data are presented on their indications, pharmacology, and the relevant end point clinical trial data with these drugs. It also discusses the human trial data on some novel therapeutic agents that are being developed including those for homozygous familial hypercholesterolemia--the antisense oligonucleotide mipomersen and the microsomal transfer protein inhibitor lomitapide. Data are presented on phase II and III trials on agents with potentially wider applications, cholesterol ester transfer protein inhibitors and proprotein convertase subtilisin kexin 9 inhibitors. The data on a licensed gene therapy for lipoprotein lipase deficiency are also presented.