Low Serum Phosphorus: A Marker for Severe Malnutrition

Hypophosphatemia is a hallmark of the refeeding syndrome, and is frequently reported in patients with anorexia nervosa. Because of this, Dr. Rollyn M. Ornstein and colleagues at Schneider Children’s Hospital, New Hyde Park, NY, recommend that all anorexic inpatients be monitored daily for serum phosphorus levels and given supplementation as needed during the first week of hospitalization. This is especially appropriate for patients who are severely malnourished, according to the authors.

Dr. Ornstein and his group reviewed the charts of 69 anorexia nervosa patients (66 females, 3 males) admitted to an inpatient adolescent medical unit between July 1998 and July 2001. They reported the results of their study at the Academy for Eating Disorders meeting in Boston in April. Mean age was 15.5 years and the mean percent of ideal body weight (IBW) was 72.7%. Serum phosphorus levels were measured daily for one week and then biweekly to weekly. Patients were started on 1200 to 1400 kcal/day, and calories were gradually increased by 200 kcal every 24 to 48 hours.

Greatest risk at very low IBW

More than a fourth of the group needed phosphorus supplementation, and the authors found that those at greatest risk weighed <70% of IBW. Overall, 27.5% of patients were treated with phosphorus supplements. Four (5%) developed moderate hypophosphatemia (<2.5 mg/dl), and 15 (21%) had mild hypophosphatemia (range: from <3.0 mg/dl to ≥ 2.5 mg/dl). Those who had moderate hypophosphatemia were significantly more malnourished than those who did not. The patient with the lowest phosphorus levels had short runs of ventricular tachycardias. According to the authors, the lowest levels of serum phosphorus generally occurred on the fourth day of hospitalization.