Bipolar disorder in the International Classification of Diseases-Eleventh version: A review of the changes, their basis, and usefulness

Table 8 The International Classification of Diseases, 11^th version field trials on reliability and clinical utility of bipolar disorder¹

Ref.	Manuscript type	Results
Formative field trials
Surveys of mental health professionals: Opinions and utilization patterns
Reed et al[22], 2011	Internet-based survey	The ICD-10 category of BD had considerable clinical utility and was commonly used. The category of single depressive disorder was commonly used and should be retained. Functional impairment should be a diagnostic criterion for mood disorders
Evans et al[151], 2013	Internet-based survey of psychologists	The ICD-10 category of BD was not as commonly used. BD was rated to have low clinical utility, especially regarding its ease of use
Avasthi et al[152], 2014	Internet-based survey	The ICD-10 category of BD was commonly used and was easy to diagnose (high ease of use)
Robles et al[153], 2014	Internet-based survey	The ICD-10 category of BD was considered a problematic diagnosis by about 4% of the participants because of its non-specificity. Only about 1% of the participants felt that BP-II disorder should be included in the current version
Maruta et al[154], 2013	Internet-based survey	A majority (69%) of the participants felt that BD should be included in a separate category of mood disorders
Studies on the clinicians’ organizational map for classifications
Roberts et al[23], 2012	Internet-based survey	Clinicians’ concepts were in keeping with the current evidence and similar across all groups and countries. BP-I, BP-II, and cyclothymic disorders were considered to be adult rather than developmental onset disorders. Clinicians’ views about the organizational structure corresponded more to the ICD-11 classification than the ICD-10 or the DSM-5
Reed et al[24], 2013	Clinic-based FTC study	Clinicians’ concepts were in keeping with the current evidence and similar across all groups and countries. Mood disorders including BP-I, BP-II, cyclothymic, depressive, and dysthymic disorders were grouped together by clinicians. This group was also among the most cohesively organized groups. The results supported the ICD-11 organization of the mood disorders group
Evaluative field trials
Studies of clinical vignettes
Gaebel et al[155], 2020	Internet-based based field study	Diagnostic accuracy of the ICD-11 BP-II disorder category was significantly higher than a modified ICD-10 BP-II category. However, regarding disorders already existing in the ICD-10, e.g., BD, there were no differences between the ICD-11 and the ICD-10. There were no significant differences in overall clinical utility of BD between the ICD-11 and the ICD-10
Kogan et al[156], 2021	Internet-based based field study	Greater diagnostic accuracy was found for the ICD-10 categories of BP-I disorder and a modified category of BP-II disorder on initial analysis. However, there were no significant differences on re-analysis. There were no significant differences between the ICD-11 and the ICD-10 categories of cyclothymic disorder. Clinical utility was somewhat lower for the ICD-11 category of BP-I disorder. Ratings of severity of depression were better with the ICD-10
Clinic-based FTC studies
Reed et al[142], 2018	ICD-11 diagnoses-reliability and utility	The clinical utility of BP-I disorder was higher than schizophrenia, schizoaffective disorder, and depressive disorders on all three parameters including diagnostic accuracy, ease of use, and clarity. Agreement between the raters was also the highest for BP-I disorder (k = 0.85)2,3
Reed et al[157], 2018	ICD-11 diagnoses-reliability	Agreement between the raters was one of the highest for BP-I disorder (k = 0.84). It was relatively low though adequate for BP-II disorder (k = 0.62)3,4
Hackmann et al[158], 2019	Qualitative study on patient perceptions of BP-I disorder	The patients commented on several additional features that were missing from the description of BP-I disorder in the ICD-11 CDR. They preferred native language and idioms. A lay language version of the diagnostic descriptions was preferred
Medina-Mora et al[159], 2019	ICD-11 diagnoses-reliability and utility	Inter-rater reliability of the mood disorders category was high (percentage agreement-87%). This was higher than schizophrenia and most of the other disorders. Clinical utility was also high
Onofa et al[160], 2019	ICD-11 diagnoses-reliability and utility	Inter-rater reliability of BP-I disorder (k = 0.83) was high. Ratings of diagnostic accuracy and ease of use were also high, but the descriptions were felt to be less useful in selecting treatment

¹Only those trials that have included results about the categories of bipolar or mood disorders are shown.

²The results were very similar to those of two ICD-10 FTC studies of clinical utility[161,162]. They were also similar to those of a clinical utility study of the DSM-5[163].

³The inter-rater reliability for a single depressive episode ranged from k values of 0.43 to 0.64. This was lower than the corresponding ICD-10 category (k = 0.66-0.73). Inter-rater reliability of recurrent depressive disorder was higher (k = 0.74) and similar to that of the ICD-10 category (k = 0.69-0.70)[161,162].

⁴The results were comparable to the BD category in the ICD-10 FTC studies (k = 0.81-0.82)[161,162]. Inter-rater reliability was also higher than that found in the DSM-5 FTC studies where reliability for BP-I disorder was 0.56 and for BP-II disorder was 0.40[164,165].

BD: Bipolar disorder; BP I: Type I bipolar disorder; BP II: Type II bipolar disorder; DSM-5: Diagnostic and Statistical Manual of Mental Disorders, 5^th edition[6]; FTC: field trial centre; ICD-10: International Classification of Diseases, 10^th version[14]; ICD-11: International Classification of Diseases, 11^th version, CDDR-Clinical Descriptions and Diagnostic Requirements[8]; k: Kappa value.