Table 3: Proportion of cases in each category of discrepancy on ICD codes showed disagreement between hospital coder and auditor.

NOS: not otherwise specified

Category	Categories of discrepancy	N (%)
1	One coder recorded a symptom while the other coder recorded a diagnosis related to the symptom. e.g. N76.0: acute vaginitis and N93.9: Abnormal uterine and vaginal bleeding, unspecified	49 (16.5)
2	Coders recorded codes for similar but not identical condition; often one coder is more specific than the other. E.g. T78.4: allergy, unspecified and T78.1: Other adverse food reactions, not elsewhere classified	62 (20.9)
3	Coders recorded obviously different codes for similar conditions. E.g. T09.5: injury of unspecified muscle and tendon of trunk, NOS and M54.5: low back pain	35 (11.8)
4	Coders recorded codes for conditions which were not similar but obviously related conditions. E.g. I49.5: sick sinus syndrome and I47.1: supraventricular tachycardia.	32 (10.8)
5	Coders recorded completely different conditions. E.g. F43.0: acute stress reaction and T48.5: poisoning by anti-common-cold drugs	49 (16.5)
6	The coders recorded different codes for the same conditions. E.g. R07.4: chest pain unspecified and R07.3: other chest pain	70 (23.6)