Apolipoprotein B causes overestimation of serum albumin concentration measured by bromocresol green method in pediatric nephrotic syndrome patients.
Yang Qin Q, Peng Wan W, Wang Wenjuan W, Feng Qiulin Q et al.
Pediatric Nephrotic syndrome (PNS) is a prevalent major disorder in children. The precise detection of albumin is of crucial significance for the diagnosis, treatment decision-making, and prognosis improvement of PNS. The bromocresol green (BCG) method is a commonly used method for clinical albumin detection. Typically, patients with PNS exhibit disordered lipid metabolism, with altered levels of apolipoprotein B (ApoB), haptoglobin (Hp), and α2-macroglobulin (α2MG), apolipoprotein A1 (ApoA1). The objective of this study was to determine whether these proteins interfere with the detection of serum albumin using the BCG method in PNS, and to evaluate the extent of interference and its clinical implications. A total of 134 PNS patients were enrolled in the study. Serum albumin levels were measured simultaneously using both the BCG method (ALB-BCG) and the immunoturbidimetric assay (ALB-ITA). In addition, serum levels of Hp, α2MG, ApoB, and ApoA1 were measured and evaluated for their potential correlation with the discrepancy in albumin measurements between the two methods (ΔALB = ALB-BCG - ALB-ITA). Furthermore, to evaluate the interference of these proteins on albumin detection using the BCG or ITA method, an in vitro interference assay was performed by spiking purified proteins into standard albumin solutions at progressively increasing concentrations, thereby assessing their potential to interfere with albumin measurement. The children were stratified into three groups based on ALB-BCG levels, Group I, ALB-BCG ≥ 25 g/L (n = 43), Group II, 20 g/L ≤ ALB-BCG < 25 g/L (n = 35), Group III, ALB-BCG < 20 g/L (n = 56). Serum albumin concentrations measured by the BCG method were significantly higher than those obtained by the ITA method, with a difference (ΔALB) ranging from 0.2 to 6.9 g/L. ΔALB showed a significant negative correlation with serum albumin levels (P < 0.01). α2MG, ApoB, Hp and ApoA1 levels showed significant differences among the three groups (P < 0.05). ΔALB demonstrated moderate correlations with Hp, α2MG, and ApoB (P < 0.001), and a weak correlation with ApoA1 (P < 0.01). In vitro experiments demonstrated that ApoB caused a dose-dependent positive interference with the serum albumin detection using the BCG method (P < 0.001), but not with the ITA method. Although α2MG can bring about a slight decrease in ALB-BCG results (P = 0.024), it does not lead to a significant alteration in ΔALB. At physiological concentrations, Hp slightly raises ALB-BCG results, thus increasing ΔALB (P = 0.007), but the changes in ΔALB are only minimal. Elevated ApoB levels lead to a dose-dependent overestimation of albumin concentration when measured using BCG method. Thus, it is advisable to utilize the ITA method for the accurate determination of serum albumin levels in PNS patients. Meanwhile, when ITA is not readily available, the bromocresol purple (BCP) method can serve as a more practical alternative. This ensures a proper assessment of colloid osmotic pressure and nutritional status, thereby facilitating clinical diagnosis and therapeutic decision-making.