Steffen Christensen

The predictive value of ICD-10 diagnostic coding used to assess Charlson comorbidity index conditions in the population-based Danish National Registry of Patients

BackgroundThe Charlson comorbidity index is often used to control for confounding in research based on medical databases. There are few studies of the accuracy of the codes obtained from these databases.We examined the positive predictive value (PPV) of the ICD-10 diagnostic coding in the Danish National Registry of Patients (NRP) for the 19 Charlson conditions.MethodsAmong all hospitalizations in Northern Denmark between 1 January 1998 and 31 December 2007 with a first-listed diagnosis of a Charlson condition in the NRP, we selected 50 hospital contacts for each condition. We reviewed discharge summaries and medical records to verify the NRP diagnoses, and computed the PPV as the proportion of confirmed diagnoses.ResultsA total of 950 records were reviewed. The overall PPV for the 19 Charlson conditions was 98.0% (95% CI; 96.9, 98.8). The PPVs ranged from 82.0% (95% CI; 68.6%, 91.4%) for diabetes with diabetic complications to 100% (one-sided 97.5% CI; 92.9%, 100%) for congestive heart failure, peripheral vascular disease, chronic pulmonary disease, mild and severe liver disease, hemiplegia, renal disease, leukaemia, lymphoma, metastatic tumour, and AIDS.ConclusionThe PPV of NRP coding of the Charlson conditions was consistently high.

Use of bisphosphonates among women and risk of atrial fibrillation and flutter: population based case-control study

Objective To assess the association between atrial fibrillation and flutter and use of bisphosphonates for osteoporosis among women. Design Population based case-control study, using medical databases from Denmark. Setting Northern Denmark. Participants 13 586 patients with atrial fibrillation and flutter and 68 054 population controls, all with complete hospital and prescription history. Main outcome measure Adjusted relative risk of atrial fibrillation and flutter. Results 435 cases (3.2%) and 1958 population controls (2.9%) were current users of bisphosphonates for osteoporosis. Etidronate and alendronate were used with almost the same frequency among cases and controls. The adjusted relative risk of current use of bisphosphonates compared with non-use was 0.95 (95% confidence interval 0.84 to 1.07). New users had a relative risk of 0.75 (95% confidence interval 0.49 to 1.16), broadly similar to the estimate for continuing users (relative risk 0.96, 95% confidence interval 0.85 to 1.09). The relative risk estimates were independent of number of prescriptions and the position of the atrial fibrillation and flutter diagnosis in the discharge record, and were similar for inpatients and outpatients. Conclusion No evidence was found that use of bisphosphonates increases the risk of atrial fibrillation and flutter.

Preadmission Use of Statins and Outcomes After Hospitalization With Pneumonia: Population-Based Cohort Study of 29 900 Patients

BACKGROUND While some experimental and clinical research suggests that statins improve outcomes after severe infections, the evidence for pneumonia is conflicting. We examined whether preadmission statin use decreased risk of death, bacteremia, and pulmonary complications after pneumonia. METHODS We conducted a population-based cohort study of 29,900 adults hospitalized with pneumonia for the first time between January 1, 1997, and December 31, 2004 in northern Denmark. Data on statin and other medication use, comorbidities, socioeconomic markers, laboratory findings, bacteremia, pulmonary complications, and death were obtained from medical databases. We used regression analyses to compute adjusted mortality rate ratios within 90 days and relative risks of bacteremia and pulmonary complications after hospitalization in both statin users and nonusers. RESULTS Of patients with pneumonia, 1371 (4.6%) were current statin users. Mortality among statin users was lower than among nonusers: 10.3% vs 15.7% after 30 days and 16.8% vs 22.4% after 90 days, corresponding to adjusted 30- and 90-day mortality rate ratios of 0.69 (95% confidence interval, 0.58-0.82) and 0.75 (0.65-0.86). Decreased mortality associated with statin use remained robust in various subanalyses and in a supplementary analysis using propensity score matching. In contrast, former use of statins and current use of other prophylactic cardiovascular drugs were not associated with decreased mortality from pneumonia. In statin users, adjusted relative risk for bacteremia was 1.07 (95% confidence interval, 0.69-1.67) and for pulmonary complications was 0.69 (0.42-1.14). CONCLUSION The use of statins is associated with decreased mortality after hospitalization with pneumonia.

Arterial cardiovascular events, statins, low-dose aspirin and subsequent risk of venous thromboembolism: a population-based case-control study.

Summary.  Background: Atherosclerotic disease has been associated with the risk of venous thromboembolism, but the available data are conflicting. There are similar confusions regarding the association of the use of aspirin and statins with venous thromboembolism. Objectives: To determine whether arterial cardiovascular events, use of statins and low‐dose aspirin were associated with the risk of venous thromboembolism. Patients and methods: In this population‐based case–control study, we identified 5824 patients with venous thromboembolism and 58 240 population controls with a complete hospital and prescription history. We used logistic regression to estimate the relative risk of venous thromboembolism, adjusted for potentially confounding factors. Results: Patients with a history of arterial cardiovascular events had a clearly increased relative risk. An event within 3 months before the index date conferred large increases in risk [relative risk 4.22 (95% confidence interval (CI), 2.33–7.64) after myocardial infarction, 4.41 (95% CI, 2.92–6.65) after stroke]. Myocardial infarction more than 3 months before the index date was not significantly associated with risk, although there was a relative risk of 1.29 (95% CI, 1.05–1.57) for myocardial infarction more than 60 months previously. A history of stroke was associated with small increases in risk after 3 months. Current use of statins was associated with a reduced risk of venous thromboembolism [relative risk = 0.74 (95% CI, 0.63–0.85)]. Aspirin use was not associated with risk. Conclusions: Patients with cardiovascular events are at a short‐term increased risk of venous thromboembolism. Statins might prevent venous thromboembolism but aspirin does not. However, as the study is non‐randomized residual confounding cannot be excluded.

Rising incidence and persistently high mortality of hospitalized pneumonia: a 10‐year population‐based study in Denmark

Background.  Little is known about temporal trends in the incidence and mortality of pneumonia in the general population.

Proton pump inhibitors and risk of gastric cancer: a population-based cohort study

Proton pump inhibitor (PPI) use leads to hypergastrinaemia, which has been associated with gastrointestinal neoplasia. We evaluated the association between PPI use and risk of gastric cancer using population-based health-care registers in North Jutland, Denmark, during 1990–2003. We compared incidence rates among new users of PPI (n=18 790) or histamine-2-antagonists (H2RAs) (n=17 478) and non-users of either drug. Poisson regression analysis was used to estimate incidence rate ratios (IRRs) adjusted for multiple confounders. We incorporated a 1-year lag time to address potential reverse causation. We identified 109 gastric cancer cases among PPI users and 52 cases among H2RA users. After incorporating the 1-year lag time, we observed IRRs for gastric cancer of 1.2 (95% CI: 0.8–2.0) among PPI users and 1.2 (95% CI: 0.8–1.8) among H2RA users compared with non-users. These estimates are in contrast to significant overall IRRs of 9.0 and 2.8, respectively, without the lag time. In lag time analyses, increased IRRs were observed among PPI users with the largest number of prescriptions or the longest follow-up compared with H2RA users or non-users. Although our results point to a major influence of reverse causation and confounding by indication on the association between PPI use and gastric cancer incidence, the finding of increased incidence among PPI users with most prescriptions and longest follow-up warrants further investigation.

Risk factors for acute renal failure requiring dialysis after surgery for congenital heart disease in children

Background:  Limited data exist on the risk factors for acute renal failure (ARF) following cardiac surgery in children with congenital heart disease. This cohort study was conducted to examine this subject, as well as changes in the incidence of ARF from 1993 to 2002, the in‐hospital mortality and the time spent in the intensive care unit (ICU).

Comparison of Charlson comorbidity index with SAPS and APACHE scores for prediction of mortality following intensive care

Background: Physiology-based severity of illness scores are often used for risk adjustment in observational studies of intensive care unit (ICU) outcome. However, the complexity and time constraints of these scoring systems may limit their use in administrative databases. Comorbidity is a main determinant of ICU outcome, and comorbidity scores can be computed based on data from most administrative databases. However, limited data exist on the performance of comorbidity scores in predicting mortality of ICU patients. Objectives: To examine the performance of the Charlson comorbidity index (CCI) alone and in combination with other readily available administrative data and three physiology-based scores (acute physiology and chronic health evaluations [APACHE] II, simplified acute physiology score [SAPS] II, and SAPS III) in predicting short- and long-term mortality following intensive care. Methods: For all adult patients (n = 469) admitted to a tertiary university–affiliated ICU in 2007, we computed APACHE II, SAPS II, and SAPS III scores based on data from medical records. Data on CCI score age and gender, surgical/medical status, social factors, mechanical ventilation and renal replacement therapy, primary diagnosis, and complete follow-up for 1-year mortality was obtained from administrative databases. We computed goodness-of-fit statistics and c-statistics (area under ROC [receiver operating characteristic] curve) as measures of model calibration (ability to predict mortality proportions over classes of risk) and discrimination (ability to discriminate among the patients who will die or survive), respectively. Results: Goodness-of-fit statistics supported model fit for in-hospital, 30-day, and 1-year mortality of all combinations of the CCI score. Combining the CCI score with other administrative data revealed c-statistics of 0.75 (95% confidence interval [CI] 0.69–0.81) for in-hospital mortality, 0.75 (95% CI 0.70–0.80) for 30-day mortality, and 0.72 (95% CI 0.68–0.77) for 1-year mortality. There were no major differences in c-statistics between physiology-based systems and the CCI combined with other administrative data. Conclusion: The CCI combined with administrative data predict short- and long-term mortality for ICU patients as well as physiology-based scores.

Risk of arterial cardiovascular diseases in patients with multiple sclerosis: a population-based cohort study.

Background: Patients with multiple sclerosis (MS) may have a higher risk of cardiovascular diseases (CVD) than the general population, but data are limited. Methods: We conducted a population-based cohort study involving Danish citizens diagnosed with MS (n = 13,963) from 1977 to 2006 and an age- and sex-matched population cohort (n = 66,407) using data on MS, arterial CVD and comorbidity from the Danish National Registry of Patients. We calculated the risk of arterial CVD for all subjects and computed adjusted incidence rate ratios (IRRs). Results: During the first year of follow-up, the risk of myocardial infarction (MI) was 0.2% among patients with MS (adjusted IRR = 1.84; 95% confidence interval, CI: 1.28–2.65, compared with population cohort members), whereas the 1-year risk of overall stroke was 0.3% (adjusted IRR = 1.96; 95% CI: 1.42–2.71). IRRs were 1.92 (95% CI: 1.27–2.90) for heart failure and 0.77 (95% CI: 0.42–1.39) for atrial fibrillation/flutter. During the subsequent 2–30 years of follow-up, IRRs remained elevated for overall stroke (1.23; 95% CI: 1.10–1.38) and heart failure (1.53; 95% CI: 1.37–1.71) but decreased for acute MI (1.10; 95% CI: 0.97–1.24). Conclusion: In this Danish cohort, the risk of CVD among MS patients was low, but greater than that in the general population, particularly in the short term.

Glucocorticoid use and risk of atrial fibrillation or flutter: a population-based, case-control study.

BACKGROUND Glucocorticoid use is associated with increased risk of myocardial infarction, stroke, and heart failure, but data are limited on the risk of atrial fibrillation or flutter. We examined whether glucocorticoid use is associated with the risk of atrial fibrillation or flutter. METHODS For this population-based, case-control study, we identified all patients with a first hospital diagnosis of atrial fibrillation or flutter from January 1, 1999, through December 31, 2005, in Northern Denmark (population, 1.7 million). For each case we selected 10 population controls matched by age and sex. We obtained data on glucocorticoid prescriptions within 60 days (current users) or longer before the index date (former users), comorbidity, and medications from medical databases. We used conditional logistic regression to compute odds ratios (ORs), controlling for potential confounders. RESULTS Among 20,221 patients with atrial fibrillation or flutter, 1288 (6.4%) were current glucocorticoid users and 2375 (11.7%) were former users. Among 202,130 population controls, 5245 (2.6%) were current glucocorticoid users and 19 940 (9.9%) were former users. Current glucocorticoid use was associated with an increased risk of atrial fibrillation or flutter compared with never use (adjusted OR, 1.92; 95% confidence interval [CI], 1.79-2.06). Among new glucocorticoid users, the adjusted OR was 3.62 (95% CI, 3.11-4.22) and among long-term users it was 1.66 (95% CI, 1.53-1.80). The increased risk remained robust in patients with and without pulmonary and cardiovascular diseases. Former glucocorticoid use was not associated with increased risk (adjusted OR, 1.00; 95% CI, 0.96-1.06). CONCLUSION Current glucocorticoid use was associated with an almost 2-fold increased risk of atrial fibrillation or flutter.