The role, yield and cost of paediatric faecal elastase-1 testing

OBJECTIVE

Faecal elastase-1 (FE1) is a sensitive marker for exocrine pancreatic enzyme insufficiency. Pancreatic insufficiency (EPI) leads to maldigestion and subsequent poor weight gain. Thus, FE1 is performed as work-up for children with failure to thrive (FTT). However, EPI in the paediatric population outside of cystic fibrosis (CF) is rare. This study aimed to identify the indications for FE1 testing and their diagnostic yield in children. The secondary aim was to evaluate the cost per case of EPI detected for the various indications.

DESIGN

All FE1 tests performed on children (0-18 years) at a tertiary paediatric hospital in Sydney, Australia between 2010 and 2013 (inclusive) were identified. A retrospective chart audit was performed to identify the indication for testing FE1. The diagnostic yield based on FE1 cut-offs <200 and < 100 μg/g were assessed.

RESULTS

The most common indication for testing FE1 was "FTT only" (71/216, 32.9%), however, in this cohort of patients, FE1 was least likely to be positive with only 2 out of the 71 (2.8%) patients returning a positive result. In comparison, CF was the second most common indication for testing (60/216, 27.8%), but nearly half (48.8%) of tests returned a positive result in this cohort. The cost per case detected (FE1 <200 μg/g) reflected the test yield with an average cost per positive test of $262.50 (AUD2015) for FTT with short-gut syndrome and $420.00 (AUD2015) for CF-related indications.

CONCLUSION

Our study shows that for patients with isolated failure to thrive, FE1 testing is low yield and costly.

A pilot study to determine the feasibility of collecting amniotic fluid samples from women during labour and measuring amniotic fluid lactate at point of care

Background

The level of lactate in amniotic fluid may provide useful clinical information when assessing progress of a woman’s labour and if so, a rapid, reliable method to assess amniotic fluid lactate is required in order to be clinically relevant. However, measuring lactate levels in amniotic fluid, using portable, handheld lactate meters may be less accurate than reference laboratory instruments designed to measure lactate levels in aqueous solutions. Prior to conducting a large study, we assessed recruitment, consent and sampling procedures, and the accuracy of a handheld lactate meter to measure lactate in amniotic fluid. We compared amniotic fluid lactate results obtained using the hand held Lactate Pro (Arkray) to results obtained using reference laboratory methods ABX Pentra 400 (Horiba).

Results

We recruited 35 nulliparous women during their antenatal hospital visits and tested amniotic fluid samples collected from 20 labouring women. The handheld Lactate Pro meter was found accurate from 9–20 mmol/L with a Passing & Bablok regression of y = 0.18 + 0.97x (95% CI 0.76–1.45). Amniotic fluid lactate results remained reliable in the presence of potential contaminants commonly encountered during labour; obstetric lubricant, blood and meconium.

Conclusion

The measurement of amniotic fluid lactate using the Lactate Pro meter was reliable compared to reference laboratory methods for measuring lactate levels in amniotic fluid. The pilot study enabled the refinement of information, recruitment, consenting and sampling procedures prior to commencing a large cohort study.

Relations between markers of renal function, coronary risk factors and the occurrence and severity of coronary artery disease

OBJECTIVE

While renal failure greatly increases coronary risk, mild renal impairment is not usually considered a major risk factor. To explore this we assessed relations between measures of mild impairment of renal function and coronary artery disease (CAD) together with other risk factors.

METHODS AND RESULTS

In 408 consecutive patients aged 75 years or less with angiographically defined normal or obstructed coronary arteries and an estimated glomerular filtration rate (eGFR) >45 mL/min per 1.73 m(2), we assessed relations between severity of CAD and levels of plasma cystatin C, creatinine, eGFR, lipid profile, C-reactive protein (CRP), homocysteine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). With univariate ANOVA, the severity of CAD was significantly associated with all indices of renal function: increased plasma cystatin C (p=0.003) and creatinine (p=0.004) and decreased eGFR (p=0.008). An elevated plasma cystatin C was associated with increases in ADMA, SDMA, CRP, homocysteine and age. ADMA, SDMA, CRP and homocysteine levels were not associated with CAD severity. eGFR was negatively associated only with SDMA and homocysteine. In multivariate analysis, increased plasma cystatin C predicted both the occurrence and the severity of CAD more strongly than other measures of renal function.

CONCLUSIONS

We conclude that mild renal impairment detected by elevated cystatin C is associated with both the occurrence and the severity of CAD, independent of the other risk factors we measured and that mild renal impairment results in increased plasma levels of homocysteine, ADMA and SDMA. Our findings suggest a possible mechanistic link between CAD and mild renal impairment in which cystatin C may serve as an early marker for CAD and may also participate directly in atherogenesis.