Vijaya Sundararajan

Coding algorithms for defining comorbidities in ICD-9-CM and ICD-10 administrative data.

Objectives:Implementation of the International Statistical Classification of Disease and Related Health Problems, 10th Revision (ICD-10) coding system presents challenges for using administrative data. Recognizing this, we conducted a multistep process to develop ICD-10 coding algorithms to define Charlson and Elixhauser comorbidities in administrative data and assess the performance of the resulting algorithms. Methods:ICD-10 coding algorithms were developed by “translation” of the ICD-9-CM codes constituting Deyos (for Charlson comorbidities) and Elixhausers coding algorithms and by physicians’ assessment of the face-validity of selected ICD-10 codes. The process of carefully developing ICD-10 algorithms also produced modified and enhanced ICD-9-CM coding algorithms for the Charlson and Elixhauser comorbidities. We then used data on in-patients aged 18 years and older in ICD-9-CM and ICD-10 administrative hospital discharge data from a Canadian health region to assess the comorbidity frequencies and mortality prediction achieved by the original ICD-9-CM algorithms, the enhanced ICD-9-CM algorithms, and the new ICD-10 coding algorithms. Results:Among 56,585 patients in the ICD-9-CM data and 58,805 patients in the ICD-10 data, frequencies of the 17 Charlson comorbidities and the 30 Elixhauser comorbidities remained generally similar across algorithms. The new ICD-10 and enhanced ICD-9-CM coding algorithms either matched or outperformed the original Deyo and Elixhauser ICD-9-CM coding algorithms in predicting in-hospital mortality. The C-statistic was 0.842 for Deyos ICD-9-CM coding algorithm, 0.860 for the ICD-10 coding algorithm, and 0.859 for the enhanced ICD-9-CM coding algorithm, 0.868 for the original Elixhauser ICD-9-CM coding algorithm, 0.870 for the ICD-10 coding algorithm and 0.878 for the enhanced ICD-9-CM coding algorithm. Conclusions:These newly developed ICD-10 and ICD-9-CM comorbidity coding algorithms produce similar estimates of comorbidity prevalence in administrative data, and may outperform existing ICD-9-CM coding algorithms.

Updating and Validating the Charlson Comorbidity Index and Score for Risk Adjustment in Hospital Discharge Abstracts Using Data From 6 Countries

With advances in the effectiveness of treatment and disease management, the contribution of chronic comorbid diseases (comorbidities) found within the Charlson comorbidity index to mortality is likely to have changed since development of the index in 1984. The authors reevaluated the Charlson index and reassigned weights to each condition by identifying and following patients to observe mortality within 1 year after hospital discharge. They applied the updated index and weights to hospital discharge data from 6 countries and tested for their ability to predict in-hospital mortality. Compared with the original Charlson weights, weights generated from the Calgary, Alberta, Canada, data (2004) were 0 for 5 comorbidities, decreased for 3 comorbidities, increased for 4 comorbidities, and did not change for 5 comorbidities. The C statistics for discriminating in-hospital mortality between the new score generated from the 12 comorbidities and the Charlson score were 0.825 (new) and 0.808 (old), respectively, in Australian data (2008), 0.828 and 0.825 in Canadian data (2008), 0.878 and 0.882 in French data (2004), 0.727 and 0.723 in Japanese data (2008), 0.831 and 0.836 in New Zealand data (2008), and 0.869 and 0.876 in Swiss data (2008). The updated index of 12 comorbidities showed good-to-excellent discrimination in predicting in-hospital mortality in data from 6 countries and may be more appropriate for use with more recent administrative data.

Quality of diagnosis and procedure coding in ICD-10 administrative data.

Objectives:The International Classification of Disease, 10th Revision (ICD-10) was introduced worldwide beginning in the late 1990s. Because there have been no published data on the quality of coding using ICD-10, the aim of our analysis is to assess the quality of ICD-10 coding in routinely collected hospital discharge data from Australia, which began using ICD-10 in 1998. Methods:Audit data from the years 1998–1999 (n = 7004) and 2000–2001 (n = 7631), excluding same-day chemotherapy and dialysis cases, were used in data analysis. Quality measures included prevalence comparisons, sensitivity, positive predictive value (PPV), and the kappa statistic. Results:Comparison of the audit sample to public hospital discharges showed little difference in age and gender, with audited cases more likely to be overnight stays. There was no difference in the median number of hospital assigned diagnosis and procedure codes per discharge. Agreement of the principal diagnosis code was 85% at the 3-digit level and 79% at the 4-digit level in 1998–1999; this rate had improved to 87% and 81% in 2000–2001. Principal procedure code agreement was 85% in 1998–1999 and 83% in 2000–2001 at the 5-digit level, and 81% and 80% at the 7-digit level, respectively. Specific major diagnoses, comorbid diagnoses, major procedures, and minor procedures showed good-to-excellent coding quality. Conclusions:The transition to ICD-10 has occurred with no loss of data quality, with data showing a high level of reliability and adherence to coding standards. When consideration is given to the nature of the analysis, administrative data can provide highly reliable population-based estimates of hospitalization rates.

Use of Adjuvant Chemotherapy and Radiation Therapy for Rectal Cancer Among the Elderly: A Population-Based Study

PURPOSE Combined adjuvant fluorouracil (5-FU)-based chemotherapy with radiation is now the standard of care for locally advanced rectal cancer in the United States. We investigated the use of these treatments for stages II and III rectal cancer among the elderly and the effectiveness of these treatments on a population-based scale. PATIENTS AND METHODS The linked Surveillance, Epidemiology, and End-Results-Medicare database was used to identify 1,807 Medicare beneficiaries > or = 65 years of age with stage II or III rectal cancer who underwent surgical resection between 1992 and 1996. We excluded members of a health maintenance organization in the 12 months before or 4 months after their diagnosis and those who died within 4 months of diagnosis. We used multivariate analysis to identify factors associated with combined 5-FU and radiation therapy, and propensity score methodology to determine survival benefit for those treated. RESULTS We found that 37% of patients received both adjuvant 5-FU and radiation therapy, 11% 5-FU alone, and 14% radiation alone. Decreasing age, increasing lymph node positivity, comorbid conditions, and nonblack race were associated with increased probability of treatment with 5-FU and radiation. Combined chemotherapy/radiation therapy was associated with improved survival for stage III (relative risk, 0.71; 95% confidence interval, 0.56 to 0.90), but not for stage II rectal cancer (relative risk, 0.89; 95% confidence interval, 0.70 to 1.14). CONCLUSION The association of combined treatment with improved survival in node-positive disease was similar to that observed in other studies. In the absence of data from well-designed randomized controlled trials, our observational data support efforts on the part of clinicians to make appropriate referrals and provide combined treatment for elderly patients with stage III rectal cancer.

Cross-national comparative performance of three versions of the ICD-10 Charlson index.

Objective:The Charlson comorbidity index has been widely used for risk adjustment in outcome studies using administrative health data. Recently, 3 International Statistical Classification of Diseases, Tenth Revision (ICD-10) translations have been published for the Charlson comorbidities. This study was conducted to compare the predictive performance of these versions (the Halfon, Sundararajan, and Quan versions) of the ICD-10 coding algorithms using data from 4 countries. Methods:Data from Australia (N = 2000–2001, max 25 diagnosis codes), Canada (N = 2002–2003, max 16 diagnosis codes), Switzerland (N = 1999–2001, unlimited number of diagnosis codes), and Japan (N = 2003, max 11 diagnosis codes) were analyzed. Only the first admission for patients age 18 years and older, with a length of stay of ≥2 days was included. For each algorithm, 2 logistic regression models were fitted with hospital mortality as the outcome and the Charlson individual comorbidities or the Charlson index score as independent variables. The c-statistic (representing the area under the receiver operating characteristic curve) and its 95% probability bootstrap distribution were employed to evaluate model performance. Results:Overall, within each populations data, the distribution of comorbidity level categories was similar across the 3 translations. The Quan version produced slightly higher median c-statistics than the Halfon or Sundararajan versions in all datasets. For example, in Japanese data, the median c-statistics were 0.712 (Quan), 0.709 (Sundararajan), and 0.694 (Halfon) using individual comorbidity coefficients. In general, the probability distributions between the Quan and the Sundararajan versions overlapped, whereas those between the Quan and the Halfon version did not. Conclusions:Our analyses show that all of the ICD-10 versions of the Charlson algorithm performed satisfactorily (c-statistics 0.70–0.86), with the Quan version showing a trend toward outperforming the other versions in all data sets.

Variations in the Use of Chemotherapy for Elderly Patients With Advanced Ovarian Cancer: A Population-Based Study

PURPOSE Since 1986, the recommended therapy for patients with ovarian cancer has included surgery and chemotherapy with a platinum compound (cisplatin or carboplatin). The purpose of this study is to assess the use of chemotherapy in elderly patients with advanced ovarian cancer. METHODS The Surveillance, Epidemiology, and End Results-Medicare database represents approximately 14% of the United States population and provides clinical and demographic information on cancer patients covered by Medicare, along with health care-utilization data from Medicare claims files. We analyzed the association of demographic and clinical factors with treatment among patients diagnosed from 1992 to 1996 with stage III or IV ovarian cancer, who survived > or = 120 days beyond diagnosis, and were > or = 65 years of age (N = 1,775). RESULTS Approximately 83% of elderly patients received some form of chemotherapy within 4 months of diagnosis. In a multiple logistic regression model with patients aged 65 to 69 years as the reference, the odds ratios of receiving chemotherapy were 0.96 (95% confidence interval [CI], 0.63 to 1.46) for ages 70 to 74, 0.65 (95% CI, 0.43 to 1.00) for 75 to 79, 0.24 (95% CI, 0.15 to 0.37) for 80 to 84, and 0.12 (95% CI, 0.07 to 0.19) for 85+. Hispanic patients were less likely to receive chemotherapy than non-Hispanic white patients. Since 1992, paclitaxel has gradually replaced cyclophosphamide as the drug most commonly used with platinum. CONCLUSION Despite its proven efficacy in treating ovarian cancer, chemotherapy seems to be used less among patients over age 65, especially those who are nonwhite and/or in the oldest age groups. Further research is needed to elucidate to what degree this represents appropriate clinical judgment and to what degree other factors, such as patient choice, play a role.

Identifying priorities in methodological research using ICD-9-CM and ICD-10 administrative data: report from an international consortium

BackgroundHealth administrative data are frequently used for health services and population health research. Comparative research using these data has been facilitated by the use of a standard system for coding diagnoses, the International Classification of Diseases (ICD). Research using the data must deal with data quality and validity limitations which arise because the data are not created for research purposes. This paper presents a list of high-priority methodological areas for researchers using health administrative data.MethodsA group of researchers and users of health administrative data from Canada, the United States, Switzerland, Australia, China and the United Kingdom came together in June 2005 in Banff, Canada to discuss and identify high-priority methodological research areas. The generation of ideas for research focussed not only on matters relating to the use of administrative data in health services and population health research, but also on the challenges created in transitioning from ICD-9 to ICD-10. After the brain-storming session, voting took place to rank-order the suggested projects. Participants were asked to rate the importance of each project from 1 (low priority) to 10 (high priority). Average ranks were computed to prioritise the projects.ResultsThirteen potential areas of research were identified, some of which represented preparatory work rather than research per se. The three most highly ranked priorities were the documentation of data fields in each countrys hospital administrative data (average score 8.4), the translation of patient safety indicators from ICD-9 to ICD-10 (average score 8.0), and the development and validation of algorithms to verify the logic and internal consistency of coding in hospital abstract data (average score 7.0).ConclusionThe group discussions resulted in a list of expert views on critical international priorities for future methodological research relating to health administrative data. The consortiums members welcome contacts from investigators involved in research using health administrative data, especially in cross-jurisdictional collaborative studies or in studies that illustrate the application of ICD-10.

Epidemiology of sepsis in Victoria, Australia

Objective:To determine the clinical and epidemiologic characteristics of patients with sepsis admitted to hospitals in Victoria, Australia, including the incidence of sepsis and severe sepsis, utilization of intensive care unit (ICU) resources, and hospital mortality. Design:A population-based hospital morbidity database generated from hospital discharge coding. Setting:State of Victoria, Australia (population, 4.5 million), the 4-yr period from July 1, 1999, to June 30, 2003. Patients:A total of 3,122,515 overnight hospitalizations. Interventions:None. Measurements and Main Results:The overall hospital incidence of sepsis was 1.1%, with a mortality of 18.4%. Of septic patients, 23.8% received some care in an ICU. For these patients, hospital mortality was 28.9%. Severe sepsis, defined by sepsis and at least one organ dysfunction, occurred in 39% of sepsis patients and was accompanied by a hospital mortality of 31.1%. Fifty percent of patients with severe sepsis received at least some care in an ICU. Conclusions:Australian state hospital administrative data reveal epidemiologic features of sepsis and severe sepsis that are strikingly similar to those recently reported from comparable populations in North American and Europe. This suggests that lessons learned in this area may be directly applicable internationally.

Accuracy of the Australian National Death Index: comparison with adjudicated fatal outcomes among Australian participants in the Long-term Intervention with Pravastatin in Ischaemic Disease (LIPID) study.

Objective: To assess the accuracy of the Australian National Death Index (NDI) in identifying deaths and recording cardiovascular and cancer causes of death.

Respiratory Tract Infections in Travelers: A Review of the GeoSentinel Surveillance Network

Respiratory tract infections are common in travelers, and improving our knowledge of risk factors associated with specific types of respiratory infections should enable implementation of better preventive strategies. Data collected by the GeoSentinel surveillance network were analyzed, and the most significant predictors for developing specific categories of respiratory infections while abroad were age, sex, season of travel, trip duration, and reason for travel. In particular, influenza was associated with travel to the Northern Hemisphere during the period of December through February, travel involving visits to friends or relatives, and trip duration of >30 days. Lower respiratory tract infections were associated with male sex and increasing age. Knowledge of the respiratory tract infections that occur in specific groups of travelers allows for the development of targeted pretravel preventive strategies to high-risk groups.