Abstract
Both DSM-5 and ICD-11 have provided weight cut-offs and severity specifiers for the diagnosis of anorexia nervosa (AN) in childhood, adolescence and adulthood. The aims of the current study focusing on inpatients aged < 19 years were to assess (1) the relationship between age and body mass index (BMI; kg/m2), BMI-centiles, BMI-standard deviation scores (BMI-SDS) and body height-SDS at referral, (2) the percentages of patients fulfilling the DSM-5 and ICD-11 weight criteria and severity categories for AN, and (3) the validity of the AN severity specifiers via analysis of both weight related data at discharge and inpatient treatment duration. The German Registry for Anorexia Nervosa encompassed complete data sets for 469 female patients (mean age = 15.2 years; range 8.9–18.9 years) with a diagnosis of AN (n = 404) or atypical AN (n = 65), who were ascertained at 16 German child and adolescent psychiatric hospitals. BMI at referral increased up to age 15 to subsequently plateau. Approximately one tenth of all patients with AN had a BMI above the fifth centile. The ICD-11 specifier based on a BMI-centile of 0.3 for childhood and adolescent AN entailed two equally sized groups of patients. Discharge data revealed limited validity of the specifiers. Height-SDS was not correlated with age thus stunting had no impact on our data. We corroborate the evidence to use the tenth instead of the fifth BMI-centile as the weight criterion in children and adolescents. Weight criteria should not entail major diagnostic shifts during the transition from adolescence to adulthood. The severity specifiers based on BMI or BMI-centiles do not seem to have substantial clinical validity.
Highlights
Underweight, fear of weight gain, and body image disturbances represent cardinal features of anorexia nervosa (AN) [1]
The DSM-5 and ICD-11 adult severity specifiers based on absolute body mass index (BMI)-cut-offs (Table 5 and Table 6) and used inpatient treatment duration and both BMI and BMI-standard deviation scores (BMI-SDS) at discharge as proxies to assess the clinical validity of the different severity categories. Both BMI and BMI-SDS at referral are clearly age dependent in young inpatients with acute AN, with the correlations being positive for BMI and negative for BMI-SDS
Our sample included 34 patients aged < 12 years, for whom we found the highest correlation (r ≈ 0.5; Fig. 2) between age and BMI; this correlation drops in the oldest age groups to approach zero as of age 15 (Table 2)
Summary
Underweight, fear of weight gain, and body image disturbances represent cardinal features of anorexia nervosa (AN) [1]. Whereas no cut-off is provided in the A criterion, the main text states that the body mass index (BMI; kg/m2) is a “useful measure to assess body weight for height” [1]. A BMI above 18.5 kg/ m2 “might be considered to have significantly low weight if clinical history or other physiological information supports this judgement” [1]. For childhood and adolescent patients, DSM-5 refers to the CDC definition of underweight based on a “BMI-for-age below the fifth centile” [1]. The main text cautiously states that clinicians need to consider “available numerical guidelines, as well as the individual’s body build, weight history, and any physiological disturbance” [1] in judging the weight of a young patient; somewhat higher cut-offs may be appropriate for individual patients. BMI-centiles were introduced to allow comparability of body weight adjusted for height across childhood and adolescence in light of the age dependency of absolute BMIvalues; Hebebrand and coworkers had initially suggested replacement of the DSM-IV weight criterion (body weight less than 85% of that expected) with the 10th BMI-centile in 1996 [2]
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