Estimation of Iron Overload-Implications of its Non-linear Correlation

Thalassaemias and haemoglobinopathies contribute the highest number of cases, as far as single gene disorders are concerned, where blood transfusion and iron chelation remain the mainstays of therapy. Depending upon the requirement of transfusion, thalassaemias have been classified into two categories: 1) Transfusion dependent, 2) Non-transfusion dependent. Non-transfusion dependent thalassaemia patients, contrary to previous belief, suffer from iron overload. If this iron is estimated by the level of ferritin in serum, it does not linearly correlate to hepatic and/or cardiac iron. It was noted during our study that serum ferritin levels up to 300 ng/ml correlated with hepatic iron load of up to 3 mg/g of DLT almost linearly, within +0.5 SD of mean. There were a few patients in whom the serum ferritin level compared to the corresponding hepatic iron content (as measured by MRI) was more than +1.0 SD, and in some patients it was even ≥ 2.5 SD. In addition to serum ferritin, which is also a marker of acute inflammation, CRP was also estimated. It was seen that in these patients, CRP was also high. They were investigated for Hepatitis B, C and work ups were done for Tuberculosis. Out of the 350 such patients who were examined, 18 patients (5.14%) had their level of serum ferritin ≥ 1.0 SD, 08 tested positive for Tuberculosis, and 05 tested Positive for Hepatitis C and 01 for Hepatitis B. 14 patients out of the 18 (77.77%), who were screened to be out of the limits of SD had some infectious pathology in addition to their primary disorder, which was detected due to this observed discrepancy. They are undergoing treatment as appropriate for the diagnosis. In conclusion, in the range where the level of serum ferritin is linearly correlated to the corresponding hepatic iron, the value was >1.0 SD of mean, clinical investigations should be done to exclude possibilities of infections like Hepatitis and Tuberculosis.