Abstract
The routine chemical assays are affected by sample haemolysis, icterus and lipaemia, collectively known as serum indices; however, little attention has been given to the consequences of these conditions on hormonal assays (immunoassays). In this study, we assess the impact of interferences from exogenous serum indices on various endocrine assays performed on the Abbott Architect i2000 system. The pool of 20 serum samples was derived from a hospitalised population. The diluted serum samples were spiked with red cell haemolysate, Intralipid and bilirubin. The interferences were studied at baseline; 12.5%, 25%, 50%, 75% and 100% of 5.0 g/L haemoglobin; 1% of 20% Intralipid; and 0.342 mmol/L of bilirubin according to the EP7-A2 guideline (Interference Testing in Clinical Chemistry; CLSI, USA). Aliquots were analysed in duplicate and/or triplicate for various hormones on the Abbott Architect i2000 immunoassay analyser. Serum ferritin (r
2
=0.84; P=0.074) and TSH (r
2
=0.81; P=0.52) levels showed a direct relationship with haemolysis and therefore overestimated because of the effects of haemolysis. The vitamin B
12
level progressively decreased as the amount of haemolysis increased (r
2
=-0.76; P=0.136). There was a significant decrease in progesterone concentration owing to lipaemia (r
2
=-0.983; P=0.003). For icteric interferences, a strong inverse correlation was observed for folic acid and was shown to be statistically significant (r
2
=-0.94; P=0.017). Assays for ferritin, TSH, vitamin B
12
, folic acid and progesterone showed various degrees of interference because of the variability in serum indices.