Arthritis is common to the six frequent chronic conditions and FCI approach, although the six frequent chronic conditions approach separates rheumatoid arthritis and osteoarthritis into individual categories.
Using the FCI, diabetes (6%), heart disease (5%) and neurological disease (5%) were most prevalent, while "other" conditions (34%) were most common using the six frequent chronic conditions described by Haagsma et al. (Table 3).
Adjustment for the specific conditions showed little improvement over adjustment based on the number of conditions represented for the ICD-10 chapters, FCI and the six frequent chronic conditions reported by Haagsma et al., supporting methods of adjustment previously used [ 10, 11, 15, 16].
The ICD-10 chapter, six frequent chronic conditions and FCI do not weight the severity of comorbidities.
Number of the six frequent chronic conditions described by Haagsma et al. [ 7] represented categorised as 0, 1, ≥ 2 v.
The AUC was higher for the number of ICD-10 chapters represented when compared to the number of the six frequent chronic conditions represented (Χ1 = 8.75, p = 0.003).
Therefore, we were not able to assess the agreement between self-report and ICD-10 coding, or fully evaluate the relationship between the FCI and the six frequent chronic conditions not prevalent in the ICD-10 codes, highlighting issues with adapting self-report based indices (e.g. the six frequent chronic conditions described by Haagsma et al). to ICD-10 based datasets.
The six frequent chronic conditions described by Haagsma et al. [ 7] also uses all available ICD-10 comorbidity codes but only six specific diagnoses are included, with all remaining comorbidities grouped together in an "other" category.
For example, the six frequent common conditions approach bundles all diagnoses related to heart disease into a single category, while the FCI separates heart disease into three categories; angina, congestive heart failure (CHF /heart disease, and heart attack.
