Lack of correlation between fecal elastase-1 levels and fecal nitrogen excretion in preterm infants

13C-Mixed Triglyceride Breath Test and Fecal Elastase as an Indirect Pancreatic Function Test in Cystic Fibrosis Infants

BACKGROUND

The 'gold standard' test for the indirect determination of pancreatic function status in infants with cystic fibrosis (CF), the 72-hour fecal fat excretion test, is likely to become obsolete in the near future. Alternative indirect pancreatic function tests with sufficient sensitivity and specificity to determine pancreatic phenotype need further evaluation in CF infants.

OBJECTIVE

Evaluation of the clinical utility of both the noninvasive, nonradioactive C-mixed triglyceride (MTG) breath test and fecal elastase-1 (FE1) in comparison with the 72-hour fecal fat assessment in infants with CF.

METHODS

C-MTG breath test and the monoclonal and polyclonal FE1 assessment in stool was compared with the 72-hour fecal fat assessment in 24 infants with CF. Oral pancreatic enzyme substitution (PERT; if already commenced) was stopped before the tests.

RESULTS

Sensitivity rates between 82% and 100% for CF patients with pancreatic insufficiency assessed by both the C-MTG breath test and the FE1 tests proved to be high and promising. The C-MTG breath test (31%-38%) as well as both FE1 tests assessed by the monoclonal (46%-54%) and the polyclonal (45%) ELISA kits, however, showed unacceptably low-sensitivity rates for the detection of pancreatic-sufficient CF patients in the present study.

CONCLUSIONS

The C-MTG breath test with nondispersive infrared spectroscopy (NDIRS) technique, as well as both FE1 tests, are not alternatives to the fecal fat balance test for the evaluation of pancreatic function in CF infants during the first year of life.

Protracted maturation of pancreatic-specific elastase 1 excretion in preterm infants of extremely low gestational age

OBJECTIVES

The aim of the present study was to better understand the exocrine pancreatic function of extremely preterm infants.

METHODS

Pancreatic-specific elastase 1 (PSE1) activity was determined in spot stool samples of 69 preterm infants of gestational age <32 weeks and birth weight <1250 g. Assays were conducted on samples collected at 2 (N = 56), 4 (N = 46), and 6 weeks of age (N = 23).

RESULTS

PSE1 activity increased from week 2 (median [interquartile range] 84 [48-187] μg/g) to week 4 (164 [87-251 μg/g; P < 0.001) but not thereafter (169 [82-298] μg/g at week 6). The maturational increase in PSE1 activity was observed only in infants of gestational age <28 weeks (P < 0.001). At 2 weeks after birth, PSE1 levels were lower in infants of gestational age <28 weeks than in infants of gestational age ≥ 28 weeks (77 [43-110] vs 165 [56-300] μg/g; P = 0.019), but this difference was less pronounced at 4 weeks (153 [77-226] vs 230 [108-503] μg/g; P = 0.070) and had disappeared by 6 weeks (163 [76-258] vs 175 [85-418] μg/g; P = 0.576). In infants on full enteral feeding regimens 4 weeks after birth, PSE1 levels were associated with weight gain per unit of energy intake (Rs = 0.431; P = 0.005). This measure of weight gain was lower (P = 0.040) in infants with PSE1 levels <200 μg/g (0.110 [0.081-0.139] g/kcal, N = 25) than in those with PSE1 levels ≥ 200 μg/g (0.139 [0.117-0.157] g/kcal, N = 15). Administration of pancreatic enzymes to infants showing PSE1 excretion levels <200 μg/g did not enhance weight gain.

CONCLUSIONS

: Extremely preterm infants have limited exocrine pancreatic function during the first weeks of life, which may contribute to growth failure.