Differential Effects of BMI Adjustment on Ferritin Levels in Anemic Patients

The prevalence of obesity and anaemia is consistently increasing in India. Obesity is a chronic inflammatory state and is associated with dysregulation of iron homeostasis. Ferritin, a marker for cellular iron stores, is also an acute phase reactant that remains elevated during inflammation. Previous studies have used inflammation-adjusted serum ferritin to address this. This current study aims to calculate body mass index (BMI)-adjusted ferritin using a regression correction and evaluate its effects across gender and BMI category in anemic patients.

De-identified data were retrieved from hospital records and laboratory information systems. BMI-adjusted ferritin was estimated using a regression correction formula: ln(adjusted ferritin) = ln(unadjusted ferritin) - β(BMI - median BMI).

A total of 458 subjects were included, of whom 62% were female and 95% were anemic. Adjusted ferritin levels were slightly lower than unadjusted levels in the normal BMI group (59.8 vs 60) and in males (102.3 vs 113.75). In contrast, adjusted ferritin levels were marginally higher in the overweight/obese group (29.9 vs 28.9) and in females (22.7 vs 22.1). The percentage change in ferritin following adjustment ranged from -0.33 to 10.07.

BMI-based regression correction had differential effects across BMI categories and gender. The adjustment substantially attenuated higher ferritin levels in normal BMI and males. In contrast, a minimal increase was observed in overweight/obese individuals and in females with lower baseline ferritin levels. Notably, the magnitude of these percentage change in ferritin is small relative to the reported within-person biological variation (BV) of ferritin, suggesting limited clinical impact.