Acid steatocrit in the first 2 years of life: diagnostic accuracy and reference limits

Introduction. The measurement of acid steatocrit (AS) is an established method to assess faecal fat balance. However, data regarding AS in healthy infants and toddlers are sparse. Aim. This study aimed to determine the range of normal values for AS in the first two years of life and evaluate the correlations with other faecal fat balance tests.Material and Methods. AS (%) was assessed by 72-hour stool collection in 160 children aged 1–24 months (8 groups of 20: aged 1–3, 4–6 months, etc.).Results. AS was higher in infants < 6 months than in those aged 7–12, 13–18 and 19–24 months (p < 0.05, p < 0.001 and p < 0.001, respectively). The correlations between AS and age and faecal fat concentration (FFC) were statistically significant, but moderate or weak (r = -0.48, p < 0.0001; r = 0.28, p < 0.001, respectively). A 90th/95th percentile nomogram of AS was created based on these results, with values ranging from 23.6/23.9% at 1 month to 12.1/12.9% at 24 months. Conclusions. Healthy infants have a significantly higher AS than older children. For this reason, we propose an upper limits nomogram, providing detailed reference values for infants and children in their first two years of life. However, it should be noted that AS does not reflect adequately FFE and FFC in this population.