PAB has a half-life of 1.9 days. It increases with restoration of nutritional status at a daily rate of more than 1 mg/dl. A PAB concentration below 8 mg/dl is common with severe PCM deficits. A serum PAB between 10 and 16 mg/dl identifies moderate PCM and patients likely to benefit from early nutritional support. Patients with cancer, liver disease, kidney disease, diabetes, digestive or absorptive disease, severe trauma or burns, obese patients who may have protein malnutrition with caloric surplus, and elderly patients are at risk for developing some forms of malnutrition. PCM either primary or associated with some other condition, has been associated with increased morbidity, mortality, and susceptibility to infection. Reference limits in infants and children are lower and age-dependent.