Eighty-five per cent of what? Discrepancies in the weight cut-off for anorexia nervosa substantially affect the prevalence of underweight.
BACKGROUND
DSM-IV cites <85% of expected body weight (EBW) as a guideline for the diagnosis of anorexia nervosa (AN) but does not require a specific method for calculating EBW. The purpose of the present study was to determine the degree to which weight cut-off calculations vary across studies, and to evaluate whether differential cut-offs lead to discrepancies in the prevalence of individuals who are eligible for the AN diagnosis.


METHODS
Two coders independently recorded the EBW calculation methods from 99 studies that either (a) compared individuals with AN to those with subclinical eating disorders or (b) conducted AN treatment trials. Each weight cut-off was applied to a nationally representative (n=12001) and treatment-seeking (n=189) sample to determine the impact of EBW calculation on the proportion who met the AN weight criterion.


RESULTS
Coders identified 10 different EBW methods, each of which produced different weight cut-offs for the diagnosis of AN. Although only 0.23% of the national sample met the lowest cut-off, this number increased 43-fold to 10.10% under the highest cut-off. Similarly, only 48.1% of treatment seekers met the lowest cut-off, whereas 89.4% met the highest.


CONCLUSIONS
There is considerable variance across studies in the determination of the AN weight cut-off. Discrepancies substantially affect the proportion of individuals who are eligible for diagnosis, treatment and insurance reimbursement. However, differences may not be fully appreciated because the ubiquitous citation of the 85% criterion creates a sense of false consensus.
Thomas
J J
JJ
Department of Psychology, Yale University, New Haven, CT, USA. jjthomas@partners.org
Roberto
C A
CA
Brownell
K D
KD
D000293:Adolescent; D000328:Adult; D000368:Aged; D000856:Anorexia Nervosa / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004608:Eligibility Determination; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D010342:Patient Acceptance of Health Care; D013851:Thinness / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D014481:United States
Ann Eugen. 1952 May;16(4):316-34
14953128
Biol Psychiatry. 2001 Apr 1;49(7):644-52
11297722
Compr Psychiatry. 1994 Mar-Apr;35(2):113-23
8187474
Int J Eat Disord. 2002 Sep;32(2):146-54
12210656
J Adolesc Health. 2006 Dec;39(6):819-27
17116511
Am J Psychiatry. 2002 Mar;159(3):412-8
11870005
Br J Psychiatry. 1996 Apr;168(4):500-6
8730948
Int J Eat Disord. 1996 May;19(4):359-69
9156689
J Clin Endocrinol Metab. 2005 Mar;90(3):1428-33
15613421
Am J Psychiatry. 1999 Nov;156(11):1697-702
10553731
Int J Eat Disord. 2008 Sep;41(6):559-63
18454485
Br J Psychiatry. 2001 Mar;178:216-21
11230031
J Psychosom Res. 1998 Mar-Apr;44(3-4):435-40
9587885
Am J Psychiatry. 1995 Jan;152(1):64-71
7802123
Am J Psychiatry. 2005 Apr;162(4):741-7
15800147
Acta Psychiatr Scand. 2003 Sep;108(3):175-82
12890271
Int J Eat Disord. 2000 Dec;28(4):415-21
11054788
J Adolesc Health. 2006 Dec;39(6):800-5
17116508
Int J Eat Disord. 2007 Apr;40(3):277-84
17262817
Eat Weight Disord. 2001 Sep;6(3):121-9
11589414
J Clin Endocrinol Metab. 1995 Mar;80(3):898-904
7883849
JAMA. 2004 Jun 16;291(23):2847-50
15199035
Am J Psychiatry. 1997 Aug;154(8):1127-32
9247400
Am J Psychiatry. 2003 Nov;160(11):2046-9
14594754
Int J Eat Disord. 2005 Mar;37(2):79-91
15732072
Int J Eat Disord. 1994 Mar;15(2):165-77
8173562
N Engl J Med. 1999 Aug 5;341(6):427-34
10432328
Psychiatr Clin North Am. 2001 Jun;24(2):271-80
11416927
Psychiatry Res. 2007 Jan 15;149(1-3):215-21
17150258
Eat Behav. 2004 Jan;5(1):55-66
15000954
Am J Psychiatry. 2005 Dec;162(12):2249-55
16330587
Int J Eat Disord. 2001 Mar;29(2):224-9
11429985
Int J Eat Disord. 1995 Apr;17(3):243-9
7773261
Psychol Med. 1993 Nov;23(4):999-1017
8134523
Am J Psychiatry. 2003 May;160(5):967-72
12727702
Eat Behav. 2001 Summer;2(2):151-68
15001043
Int J Eat Disord. 2005;37 Suppl:S95-7
15852330
Int J Eat Disord. 2007 May;40(4):310-20
17370290
Am J Psychiatry. 1998 Apr;155(4):548-51
9546003