Spuriously raised serum amylase in a five-year-old girl: a note of caution in paediatric blood sampling.

INTRODUCTION: Capillary (finger prick) blood sampling is commonplace in paediatric practice but this method is prone to produce spurious laboratory results. CASE PRESENTATION: A five-year-old girl presented with abdominal pain, epigastric tenderness, tachycardia and reduced oxygen saturation. A venous blood sample haemolysed, and serum amylase on a finger prick sample was reported as 2831 units/L. The working diagnosis was acute pancreatitis and respiratory tract infection. A repeat amylase 9 h later was within the normal range. The patient was known to bite her fingers and the possibility of salivary contamination was considered. Serum isoenzyme analysis confirmed presence of high salivary amylase levels with no pancreatic amylase detected. A viral respiratory tract infection and buried gastrostomy bumper were eventually thought to account for the patient's presentation. CONCLUSION: Increased awareness of the potential for salivary contamination of serum amylase in finger prick samples may prevent misdiagnoses of pancreatitis.

Quantification of urinary sodium concentrations in term infants.

BACKGROUND: Infants with gastrointestinal conditions and poor weight gain are administered sodium supplementation based on urinary sodium concentrations. However, the reference range of urinary electrolytes is unknown. The aim of this study was to ascertain the normal values of urinary electrolytes in healthy, term infants. Secondary aims were to establish the relationship between urinary electrolytes with weight velocity and feeding practices. METHODS: Healthy, term (≥37 weeks' gestation) infants were recruited. Parental questionnaires were completed before discharge and at six weeks. Electrolytes were quantified from a urine sample at six weeks. t-Tests and Mann-Whitney U tests were conducted for parametric and non-parametric electrolytes, respectively. RESULTS: A total of 200 infants were recruited before discharge. Twenty-nine follow-up questionnaires and urine samples were returned (nine female; mean gestational age 39 + 6 weeks [SD 9.9 days]; mean birthweight 3350 g [SD 483 g]; 17 breastfed, nine formula and three mixed; mean change in Z score for weight -0.914 [SD 0.814]). Majority (25/29) of infants had urinary sodium <20 mmo/L. Change in Z score for weight was similar between infants with sodium <20 mmol/L and >20 mmol/L ( P = 0.78). All exclusively breastfed infants had sodium <20 mmol/L, however, not statistically dissimilar to formula-fed infants ( P = 0.27). CONCLUSION: Most term infants in this study had urinary sodium values <20 mmol/L with no identified relationship to weight velocity. Lower concentrations of sodium could be not quantified reliably because of the limitations of the analytical method that were used. More evidence is required to identify candidates for sodium supplementation.