Multi-centre observational study of spurious hyperkalaemia due to EDTA contamination.

BACKGROUND: A multi-centre observational study investigating the prevalence of spurious hyperkalaemia due to potassium ethylenediaminetetraacetic acid (kEDTA) contamination. METHODS: Serum EDTA was measured in anonymised serum samples with a serum potassium > 6.0 mmol/L collected over a one month period in five different hospital laboratories. Two of the participating laboratories routinely screen all hyperkalaemic samples for EDTA contamination. RESULTS: EDTA contamination was present in 4.1% (range 1.2%-6.7%) of hyperkalaemic samples. In three laboratories, without routine EDTA screening, 50% "EDTA contaminated" were identified by laboratory staff, the remaining 50% samples were undetected and reported as genuine hyperkalaemia. In these laboratories, EDTA was not measurable in 2 samples reported as "EDTA contaminated". CONCLUSIONS: Spurious hyperkalaemia due to kEDTA contamination is relatively common. Education regarding correct blood collection technique offers the best strategy in preventing EDTA sample contamination. Gross kEDTA contamination is easily identified by laboratory staff in samples with marked unexpected hyperkalaemia and hypocalcaemia. Spurious hyperkalaemia due to modest kEDTA contamination may only be confidently detected by measurement of serum EDTA.

Effects of hormone replacement therapy on insulin-like growth factor (IGF)-I, IGF-II and IGF binding protein (IGFBP)-1 to IGFBP-4: implications for cardiovascular risk.

OBJECTIVE: Hormone replacement therapy (HRT) in postmenopausal women is controversial, with an elevated cardiovascular event rate for combined estrogen-progestogen but no adverse cardiovascular effect and possible cumulative benefit for estrogen alone. Here we measured the effects of differing estrogen/progestogen combinations on the insulin-like growth factor (IGF)/IGF binding protein (IGFBP) system which has been implicated in the pathophysiological mechanisms underlying cardiovascular disease, higher IGFBP-1 levels having been linked with a reduced cardiovascular risk. DESIGN: Oral conjugated equine estrogens (CEE) alone, or in combination with the increasingly androgenic progestogens medroxyprogesterone acetate, desogestrel or norethisterone, were given in a randomized triple crossover fashion to 35 healthy postmenopausal women. Serum concentrations of IGFs and the principal circulating IGFBPs were measured. RESULTS: Circulating IGF-I, IGFBP-3 and IGF-I/IGFBP-3 molar ratio were significantly reduced by CEE. These effects were reversed by progestogens according to their androgenicity. Plasma IGFBP-1 concentration increased from baseline to CEE alone. This rise was opposed by progestogens of increasing androgenicity. IGFBP-2 levels fell and IGFBP-4 increased with CEE, with no further change with addition of progestogens. CEE increased the proportional contribution of IGFBP-1 and IGFBP-4 to total IGFBP binding and decreased the IGFBP-3 contribution. This was reversed by progestogens. CONCLUSION: There are marked changes in molar ratios of the IGFBPs in relation to estrogen/progestogens in HRT. The effect of progestogens on IGF bioavailability could be an important determinant of the longer-term risks of specific HRT preparations by opposing the potentially beneficial effects of CEE alone on cardiovascular risk.