Rapid turnover proteins as nutritional indicators

Abstract

Abstract Many of the commonly employed nutritional parameters are inadequate indices of malnutrition since they are relatively nonspecific, focused on depletion, have limited validity, and do not always reflect improvements after repletion. Recent studies have focused on the rapid turnover proteins (RTP), particularly thyroxin‐binding prealbumin (TBPA) and retinol‐binding protein (RBP) as more sensitive indicators of malnutrition. Twenty patients with protein‐calorie malnutrition who were given total parenteral nutrition were evaluated by routine nutritional parameters and rapid turnover protein assays for comparison. Results show statistically significant increases in mean values of TBPA ( p < 0.001) and RBP ( p < 0.0001) when compared in negative versus positive nitrogen balance (NB). Serum albumin levels decreased ( p < 0.03), while transferrin ( p < 0.03) and total lymphocyte count ( p < 0.3) demonstrated less significance when compared in negative versus positive NB. Overall RBP and TBPA levels increased 2.8–3‐fold from negative to positive nitrogen balance. In mildly malnutritioned patients TBPA levels increased from 6.14 (±3.84) mg/100 ml to 22.42 (±9.62) mg/100 ml ( p < 0.001); in moderately malnutritioned patients the TBPA increased from 7.2 (±6.68) mg/100 ml to 23.6 (±16.59) mg/100 ml ( p < 0.04); and in severe forms, TBPA increased from 6.0 (±4.58) mg/100 ml to 18.66 (±7.37) mg/100 ml ( p < 0.06). No such correlation could be found with the other routine nutritional parameters. We conclude that TBPA and RBP levels can be used as serum markers of mild to severe malnutrition and that there exists a numerical range of values for TBPA and RBP which correlates with negative and/or positive nitrogen balance.