Answer: d Since protein is the functional and structural chemical of the body, most nutritional assessment techniques are estimates of protein reserves. The actual nitrogen balance can be measured by measuring the amount of nitrogen excreted. This is most conveniently done by measuring the amount of urea excreted in the urine, assuming that urea constitutes 85% of the total nitrogen excretion. Knowing nitrogen excretion, the amount of protein catabolized can be estimated and compared with the amount of protein ingested by the patient. Indirect assessments of protein reserves are based on single measurements of body substances that are dependent on rapid protein synthesis for maintenance of normal levels. Conventional serum proteins such as albumin and globulin are not affected by malnutrition until it is very severe. Proteins such as prealbumen and transferrin, which turn over more rapidly, are better indicators of protein status. Lymphocytes are rapidly destroyed and protein is required for the formation of new cells. Consequently, the absolute lymphocyte count is a useful measure of the status of protein reserves. The lymphocyte count is considered by some the best single “static” measurement characterizing nutritional status. Protein is also required for synthesizing the cells and mediators involved in skin test reactivity. Although skin test reactivity is a manifestation of lymphocyte-mediated immunity, its usefulness in patient assessment is probably that of assessment of the inflammatory response than lymphocyte activity per se. Some chronically and acutely malnourished patients convert from reactive to anergic, and reactivity can be restored by nutritional repletion