Three- and four-digit ICD-10 is not a reliable classification system in primary care

Figures & data

Figure 1.  Chapter kappa (black) and average kappa value of all three-digit (grey) and four-digit (transparent) codes used chronic managed problems (chapters XV and XVI were summarized).

Table I.  Averaged number of cases in each ICD-10 chapter.

ICD-10 chapter		n (chronic)	n (new)
I	Infectious diseases	41	161.5
II	Neoplasms	202.5	39.5
III	Blood diseases	44.5	33.5
IV	Endocrine & metabolism	1168.5	216
V	Mental & behavioural	319.5	205.5
VI	Nervous system	179	129
VII	Eye diseases	23	47.5
VIII	Ear diseases	36	94.5
IX	Circulatory system	2817	533.5
X	Respiratory system	454	1235
XI	Digestive system	331.5	433
XII	Skin diseases	177.5	214.5
XIII	Musculoskeletal system	829	1130
XIV	Genitourinary system	92.5	146.5
XV	Pregnancy	7.5	4
XVII	Congenital malformations	34.5	5
XVIII	Symptoms & findings	68.5	222
XIX	Injuries	87.5	423
XX	External causes	0.5	351.5
XXI	Health status	17.5	161.5

Figure 2.  Chapter kappa (black) and average kappa value of all three-digit (grey) and four-digit (transparent) codes used new managed problems (chapters XV and XVI were summarized).