Trajectories of blood parameters and body weight during inpatient treatment of anorexia nervosa with extreme underweight.

BACKGROUND: Laboratory parameters and body weight are objective markers of physical stability in patients with severe and extreme anorexia nervosa. However, systematic analyses of trajectories during inpatient treatment with high-calorie refeeding and prophylactic phosphate supplementation remain limited in extremely underweight persons. Therefore, it is essential to gain a comprehensive understanding of changes in laboratory parameters, body mass index, and factors influencing these trajectories under this treatment approach in patients with severe and extreme anorexia nervosa, who are at particularly high risk of medical complications. METHODS: Retrospective data of a six-week treatment period from 519 female inpatients of a specialized care unit with anorexia nervosa (body mass index at admission: M = 12.6 kg/m2, SD = 1.35) were analyzed. Laboratory parameters (hemoglobin, thrombocytes, leukocytes, aspartate aminotransferase, alanine aminotransferase, creatine kinase, sodium, potassium, and phosphate) and body weight were assessed weekly. RESULTS: More than one-third of patients showed leukopenia or hypertransaminasemia at admission. Most laboratory values and body mass index tended to ameliorate during the six-week treatment period. Lower body mass index at admission or longer illness duration was associated with larger changes in body mass index and several laboratory parameters (e.g., hemoglobin or aspartate aminotransferase). CONCLUSIONS: These findings provide a detailed characterization of laboratory changes during inpatient refeeding with prophylactic phosphate supplementation. The observed temporal patterns of laboratory stabilization may help inform individualized monitoring strategies and provide a basis for evaluating whether the frequency of routine laboratory testing can be tailored over a longer course of treatment according to clinical status and resolution of previous abnormalities. Furthermore, these findings may support the effectiveness and safety of inpatient refeeding protocols with prophylactic phosphate supplementation in patients with severe and extreme anorexia nervosa and an extremely low body mass index at admission (< 13 kg/m2).