Accuracy of Medicare claims-based diagnosis of acute myocardial infarction: estimating positive predictive value on the basis of review of hospital records

Background

Many cardiovascular epidemiologic studies rely on diagnosis codes in health care claims databases. Despite important changes in the care and diagnosis of acute myocardial infarction (AMI), the validity of hospital discharge diagnosis codes for AMI in the US Medicare system has not been recently examined. Our objective was to examine the accuracy of International Classification of Diseases—ninth revision—Clinical Modifications (ICD-9-CM) discharge diagnosis codes and diagnosis-related groups (DRG) codes for AMI in a Medicare claims database.

Methods

We sampled hospitalization episodes from Medicare beneficiaries in Pennsylvania during 1999, 2000, or both. We used Medicare data to identify patients with hospitalizations containing indicators of AMI (ICD-9-CM diagnosis codes 410.X0 and 410.X1 or DRG codes 121, 122, and 123). Hospital records for these episodes were reviewed by trained abstractors using World Health Organization criteria for diagnosing AMI. We then calculated the positive predictive value of Medicare claims-based definitions of AMI.

Results

Of 2200 hospitalization episodes with Medicare diagnosis codes suggestive of AMI, 2022 hospital records (91.9%) were obtained. The positive predictive value for a primary Medicare claims-based definition was 94.1% (95% CI, 93.0%-95.2%). Positive predictive values for alternative claims-based definitions ranged slightly, with the definition including DRG codes and length-of-stay restrictions yielding the highest positive predictive value, 95.4% (95% CI, 94.3%-96.4%). Subjects with a history of myocardial infarction had a significantly lower positive predictive value than subjects without a history of myocardial infarction (88.1% vs 94.6%, P <.001).

Conclusions

In this study, we observed high positive predictive values for a Medicare claims-based diagnosis of AMI and a diagnosis based on structured hospital record review.     

Nonalcoholic fatty liver disease in Japanese patients with severe obesity who received laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) in comparison to non-Japanese patients

Background. The number of patients with morbid obesity is increasing worldwide. However, the prevalence of morbid obesity is still low in Japan, and therefore few systematic investigations of liver dysfunction in this population have so far been carried out. This study aimed to investigate the clinical characteristics in severe obese Japanese patients undergoing laparoscopic Roux-en-Y gastric bypass surgery (LRYGB). Methods. Eighty-four patients with severe obesity, including 61 Japanese and 23 non-Japanese patients, were analyzed. Results. The mean body mass index (BMI) was 43.7 ± 7.8 kg/m², and there was no difference between Japanese and non-Japanese patients. Nonalcoholic fatty liver disease (NAFLD) was observed in 45/59 (76.2%) of the Japanese patients. Although there were no differences in the BMI and body weight, serum ALT was higher in Japanese patients in comparison to non-Japanese patients (P < 0.05). The indices for insulin resistance were significantly higher in the Japanese patients in comparison to non-Japanese patients (P < 0.01). The liver/spleen computed tomography (CT) ratios were lower in Japanese patients (P < 0.05). The laboratory data and BMI significantly improved at 1 year after LRYGB in both groups. Conclusions. Racial difference may exist difference may exist in NAFLD in patients with severe obesity. When the BMI is similar, liver dysfunction among Japanese patients with severe obesity tends to be higher than in non-Japanese patients. Japanese patients with severe obesity must therefore reduce their body weight to a greater degree in comparison to non-Japanese patients with the same BMI. LRYGB can achieve effective weight control and lower ALT levels in Japanese patients with severe obesity.     

Coronary stent implantation in patients with a single coronary artery--a report of 3 cases

An isolated single coronary artery is a rare congenital anomaly and a cause of cardiac ischemia, congestive heart failure, and sudden cardiac death. Reported here are 3 cases of single coronary artery with acute myocardial infarction in which coronary stenting was performed. Also reported are the coronary blood flow patterns of the right coronary artery arising from the single left coronary artery.