Validation of self-reported comorbidity status of breast cancer patients with medical records: the California Breast Cancer Survivorship Consortium (CBCSC)

To develop the Self-Administered Comorbidity Questionnaire (SCQ) and assess its psychometric properties, including the predictive validity of the instrument, as reflected by its association with health status and health care utilization after 1 year. A cross-sectional comparison of the SCQ with a standard, chart abstraction-based measure (Charlson Index) was conducted on 170 inpatients from medical and surgical care units. The association of the SCQ with the chart-based comorbidity instrument and health status (short form 36) was evaluated cross sectionally. The association between these measures and health status and resource utilization was assessed after 1 year. The Spearman correlation coefficient for the association between the SCQ and the Charlson Index was 0.32. After restricting each measure to include only comparable items, the correlation between measures was stronger (Spearman r = 0.55). The SCQ had modest associations with measures of resource utilization during the index admission, and with health status and resource utilization after 1 year. The SCQ has modest correlations with a widely used medical record-based comorbidity instrument, and with subsequent health status and utilization. This new measure represents an efficient method to assess comorbid conditions in clinical and health services research. It will be particularly useful in settings where medical records are unavailable.

Questionnaires are used to estimate disease burden. Agreement between questionnaire responses and a criterion standard is important for optimal disease prevalence estimates. We measured the agreement between self-reported disease and medical record diagnosis of disease. A total of 2,037 Olmsted County, Minnesota residents > or =45 years of age were randomly selected. Questionnaires asked if subjects had ever had heart failure, diabetes, hypertension, myocardial infarction (MI), or stroke. Medical records were abstracted. Self-report of disease showed >90% specificity for all these diseases, but sensitivity was low for heart failure (69%) and diabetes (66%). Agreement between self-report and medical record was substantial (kappa 0.71-0.80) for diabetes, hypertension, MI, and stroke but not for heart failure (kappa 0.46). Factors associated with high total agreement by multivariate analysis were age 12 years, and zero Charlson Index score (P < .05). Questionnaire data are of greatest value in life-threatening, acute-onset diseases (e.g., MI and stroke) and chronic disorders requiring ongoing management (e.g.,diabetes and hypertension). They are more accurate in young women and better-educated subjects.

Postmenopausal women aged 55 years and older have 66% of incident breast tumors and experience 77% of breast cancer mortality, but other age-related health problems may affect tumor prognosis and treatment decisions. To document the comorbidity burden of postmenopausal breast cancer patients and evaluate its relationship with age on disease stage, treatment, and early mortality. Data were collected on breast cancer patients' comorbidities by retrospective hospital medical records review and merged with information on patients' tumor characteristics collected from 6 regional National Cancer Institute Surveillance, Epidemiology, and End Results cancer registries. Patients were followed up until death or for 30 months from breast cancer diagnosis. Population-based random sample of 1800 postmenopausal breast cancer patients diagnosed in 1992 stratified by 3 age groups: 55 to 64 years, 65 to 74 years, and 75 years and older. Extent of disease, therapy received, comorbidity, cause of death, and survival. Seventy-three percent (1312 of 1800) of the sample was diagnosed with stage I and II breast cancer, 10% (n = 188) with stage III and IV breast cancer, and 17% (n = 300) did not have a stage assignment. Of the 1017 patients with stage I and stage II node-negative breast cancer, 95% received therapy in agreement with the National Institutes of Health consensus statement recommendation for early-stage breast cancer. Patients in older age groups were less likely to receive therapy consistent with the consensus statement (P<.001), and women aged 70 years and older were significantly less likely to receive axillary lymph node dissection as determined by logistic regression analysis (P<.01). Diabetes, renal failure, stroke, liver disease, a previous malignant tumor, and smoking were significant in predicting early mortality in a statistical model that included age and disease stage. Breast cancer was the underlying cause of death for 135 decedents (51.3%). Heart disease (n = 45, 17.1%) and previous cancers (n = 22, 8.4%) were the next major underlying causes. In the 30-month follow-up period, 263 patients (15%) died. Patient care decisions occur in the context of breast cancer and other age-related conditions. Comorbidity in older patients may limit the ability to obtain prognostic information (ie, axillary lymph node dissection), tends to minimize treatment options (eg, breast-conserving therapy), and increases the risk of death from causes other than breast cancer.