Total body nitrogen as a predictor of clinical status in anorexia nervosa

It has been demonstrated that clinical outcome is positively correlated with depletion of total body nitrogen (TBN) and therefore of body protein in certain serious medical conditions such as cystic fibrosis or patients receiving dialysis for chronic renal failure. Patients with anorexia nervosa are not suffering from medical illness per se yet the illness can be chronic and severely debilitating requiring numerous hospitalizations for refeeding and/or management of medical complications. The prediction of chronicity remains an important and difficult issue that this study seeks to address by examining the correlation between several clinical indices in 18 patients suffering from anorexia nervosa with parameters of body composition, namely TBN and percentage body fat. TBN was measured using the technique of in vivo neutron-activation analysis (IVNAA) and expressed as nitrogen index. Percentage body fat was estimated using skinfold measurements. The highest correlation was between nitrogen index and number of hospitalizations (r = -.80). The data support a relationship between depletion of body nitrogen/protein and chronicity in anorexia nervosa.