The health-care databases may be a valuable source for epidemiological research in hip fracture surgery, if the diagnoses are valid. We examined the validity of hip fracture diagnoses and surgical procedure codes in the Danish Multidisciplinary Hip Fracture Registry (DMHFR) and the Danish National Patient Registry (DNPR) by calculating the positive predictive value (PPV). Methods: We identified a random sample of 750 hip fracture patients registered in the DMHFR between 2014 and 2017. Diagnoses have been coded by the 10 th revision of the International Classification of Diseases, while procedures have been coded by the Nordic Medico-Statistical Committee classification in the DNPR and directly transferred to the DMHFR. Using the surgical procedure description from the medical record as gold standard, we estimated the PPV of the hip fracture diagnoses and surgical procedure codes in the DMHFR and the DNPR with 95% confidence interval (CIs). Results: The PPV was 90% (95% CI: 86%-93%) for fracture of the neck of femur, 92% (95% CI: 87%-95%) for trochanteric fracture, and 83% (95% CI: 78%-88%) for subtrochanteric fracture. Joining trochanteric and subtrochanteric fracture resulted in a PPV of 97% (95% CI: 95%-98%). Procedure codes had a PPV of 100% for primary prosthetic replacement and internal fixation with intramedullary nail, 96% (95% CI: 85%-99%) for internal fixation using screws alone, 91% (95% CI: 84%-96%) for internal fixation using plates and screws, and 89% (95% CI: 83%-94%) for internal fixation with other or combined methods. Stratifying by age group, gender, hospital type and calendar year of surgery showed similar results as the overall PPV estimates. Conclusion: Our findings indicate a high quality of the hip fracture diagnoses and corresponding procedure codes in the DMHFR and the DNPR, with a majority of PPVs above 90%. Thus, the DMHFR and the DNPR are a valuable data source on hip fracture for epidemiological research.

Objective Comorbidity has an important role in risk prediction and risk adjustment modelling in observational studies. However, it is unknown which comorbidity index is most accurate to predict mortality in hip fracture patients. We aimed to evaluate the prediction ability, including discrimination and calibration of Charlson comorbidity index (CCI), Elixhauser comorbidity index (ECI) and Rx-risk index for 30 day- and 1 year mortality in a population-based cohort of hip fracture surgery patients. Methods Using the Danish Multidisciplinary Hip Fracture Registry in the period 2014–2018, 31,443 patients were included. CCI and ECI were based on discharge diagnoses, while Rx-Risk index was based on pharmacy dispensings. We used logistic regression to assess discrimination of the different indices, individually and in combinations, by calculating c-statistics and the contrast in c-statistic to a base model including only age and gender with 95% confidence intervals (CI). Results The study cohort were primarily female (69%) and older than 85 years (42%). The 30-day mortality was 10.1% and the 1-year mortality was 26.6%. Age and gender alone had a good discrimination ability for 30-day and 1-year mortality (c-statistic=0.70, CI: 0.69–0.71 and c-statistic=0.68, CI: 0.67 −0.69, respectively). By adding indices individually to the base model, Rx-risk index had the best 30-day and 1-year mortality discrimination ability (c-statistic=0.73, CI: 0.72–0.74 and 0.71 CI: 0.71–0.72, respectively). By adding combination of indices to the base model, a combination of CCI and the Rx-risk index had a 30-day and 1-year mortality discrimination ability of c-statistic=0.74, CI: 0.73–0.75 and c-statistic=0.73, CI: 0.73–0.74, respectively. Calibration of indices was similar. Conclusion The highest discrimination ability was achieved by combining CCI and Rx-risk index in addition to age and gender. However, age and gender alone had a fair mortality discrimination ability.

Background: The loss of pre-fracture basic mobility status is associated with increased mortality and any readmission after hip fracture. However, it is less known if the loss of pre-fracture mobility has impact on acquiring a post-discharge infection.Purpose: To examine if the loss of pre-fracture basic mobility status at hospital discharge was associated with hospital-treated or community-treated infections within 30-days of hospital discharge after hip fracture.Methods: Using the nationwide Danish Multidisciplinary Hip Fracture Registry from January 2014 through November 2017, we included 23,309 patients undergoing surgery for a first-time hip fracture. The Cumulated Ambulation Score (CAS, 0-6 points) was recorded using questionnaire at admission (pre-fracture CAS) and objectively assessed at discharge. The loss of any CAS-points at discharge compared with prefracture CAS was calculated and dichotomized (yes/no). Using Cox regression analyses, we estimated the hazard ratio (HR) with 95% confidence interval (CI) of any hospital-treated infection, hospital-treated pneumonia or community-treated infection adjusted for sex, age, body mass index, Charlson Comorbidity Index, residential status, type of fracture, and length of hospital stay (LOS).Results: Total of 12,046 (62%) patients lost their pre-fracture CAS status at discharge. Among patients who had lost their pre-fracture CAS, 6.0% developed a hospital-treated infection compared to 4% of those who did not lose their pre-fracture CAS. Correspondingly, 9.2% versus 6.2% developed a community-treated infection. The risk of 30-day post-discharge infection increased with increasing loss of any CAS points. The adjusted HRs for patients who had lost their pre-fracture CAS status, compared to patients who did not, was 1.34 (CI: 1.16-1.54) for hospital-treated infection, 1.35 (CI: 1.09 -1.67) for pneumonia and 1.36 (CI: 1.21-1.52) for community-treated infection. Conclusion:In this large national cohort study, we found that loss of pre-fracture basic mobility status upon hospital discharge was strongly associated with 30-day post-discharge risk of developing infection. These findings suggest a clinical importance of carefully focusing on regaining the pre-fracture basic mobility before discharging the patient.

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