The role of cystatin C and various methods of glomerular filtration rate calculation in evaluation of renal dysfunction in children with acute infectious diarrhea

Abstract

Rationale: Acute infectious diarrhea (AID) is the fourth leading cause of death among children < 5 years worldwide. Kidney damage is one of the poorly studied aspects of pediatric AID. The level of serum cystatin C is independent on gender and age, and it is highly informative even in the early stages of renal dysfunction.Aim: To optimize diagnosis of renal dysfunction in children with moderate AID through comparison of different methods of glomerular filtration rate (GFR) calculation and determination of serum cystatin C level.Materials and methods: Observational cross-sectional study enrolled 80 children in pediatric hospital with moderate AID not followed by hemolytic uremic syndrome. Serum creatinine and serum cystatin C levels were determined in all the patients in acute period with GFR calculating according to Schwartz equation in unmodified (1976) and modified (2009) versions. GFR was also calculated using a single-factor equation based on serum cystatin C level.Results: GFR in acute period, calculated according to unmodified and to modified Schwartz equation was in patients < 3 years (n = 40) 115.47 ± 3.33 ml/min/1.73 m2and 98.56 ± 2.84 ml/min/1.73 m2(p < 0.001), in patients 3-7 years 132.13 ± 4.2 ml/min/1.73 m2and 108.85 ± 3.84 ml/min/1.73 m2(p < 0.001), respectively. Increased serum cystatin C level (> 950 ng/ml) occurred in 18 patients (22%). In other patients level of serum cystatin C remained within the reference range or lower. The risk of acute kidney injury development based on two indicators - GFR according to the modified Schwartz equation and GFR according to the equation used cystatin C level - occurred in 4 (10%) patients aged 1-3 years and in 1 (2.5%) child in the age group 3-7 years; risk, based on one indicator - the calculation of GFR according to the formula using cystatin C - in 8 (20%) and 9 (22.5%) children, respectively, and based on the assessment of only GFR according to the modified Schwartz equation - in 3 (7.5%) children of both age groups.Conclusion: We have confirmed that the GFR values calculated with usage of unmodified Schwartz equation (1976) are higher than those calculated with usage of modified Schwartz equation (2009) and taking into account the level of cystatin C.Thus, usage of unmodified Schwartz equation for GFR calculation in infants and preschool children seems incorrect. Level of serum cystatin C is promising marker permitted to select patients with risk of acute kidney injury development among children in acute period of moderate AID.