Introduction to propensity scores: A case study on the comparative effectiveness of laparoscopic vs open appendectomy.
ABSTRACT To demonstrate the use of propensity scores to evaluate the comparative effectiveness of laparoscopic and open appendectomy.
Retrospective cohort study.
Academic and private hospitals.
All patients undergoing open or laparoscopic appendectomy (n = 21 475) in the Public Use File of the American College of Surgeons National Surgical Quality Improvement Program were included in the study. We first evaluated the surgical approach (laparoscopic vs open) using multivariate logistic regression. We next generated propensity scores and compared outcomes for open and laparoscopic appendectomy in a 1:1 matched cohort. Covariates in the model for propensity scores included comorbidities, age, sex, race, and evidence of perforation.
Patient morbidity and mortality, rate of return to operating room, and hospital length of stay.
Twenty-eight percent of patients underwent open appendectomy, and 72% had a laparoscopic approach; 33% (open) vs 14% (laparoscopic) had evidence of a ruptured appendix. In the propensity-matched cohort, there was no difference in mortality (0.3% vs 0.2%), reoperation (1.8% vs 1.5%), or incidence of major complications (5.9% vs 5.4%) between groups. Patients undergoing laparoscopic appendectomy experienced fewer wound infections (odds ratio [OR], 0.4; 95% confidence interval [CI], 0.3-0.5) and fewer episodes of sepsis (0.8; 0.6-1.0) but had a greater risk of intra-abdominal abscess (1.7; 1.3-2.2). An analysis using multivariate adjustment resulted in similar findings.
After accounting for patient severity, open and laparoscopic appendectomy had similar clinical outcomes. In this case study, propensity score methods and multivariate adjustment yielded nearly identical results.
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ABSTRACT: Objective To test the equivalence for clinical effectiveness between microdecompression and laminectomy in patients with central lumbar spinal stenosis. Design Multicentre observational study. Setting Prospective data from the Norwegian Registry for Spine Surgery. Participants 885 patients with central stenosis of the lumbar spine who underwent surgery at 34 Norwegian orthopaedic or neurosurgical departments. Patients were treated from October 2006 to December 2011. Interventions Laminectomy and microdecompression. Main outcome measures The primary outcome was change in Oswestry disability index score one year after surgery. Secondary endpoints were quality of life (EuroQol EQ-5D), perioperative complications, and duration of surgical procedures and hospital stays. A blinded biostatistician performed predefined statistical analyses in unmatched and propensity matched cohorts. Results The study was powered to detect a difference between the groups of eight points on the Oswestry disability index at one year. 721 patients (81%) completed the one year follow-up. Equivalence between microdecompression and laminectomy was shown for the Oswestry disability index (difference 1.3 points, 95% confidence interval −1.36 to 3.92, P<0.001 for equivalence). Equivalence was confirmed in the propensity matched cohort and full information regression analyses. No difference was found between groups in quality of life (EQ-5D) one year after surgery. The number of patients with complications was higher in the laminectomy group (15.0% v 9.8%, P=0.018), but after propensity matching for complications the groups did not differ (P=0.23). The duration of surgery for single level decompression was shorter in the microdecompression group (difference 11.2 minutes, 95% confidence interval 4.9 to 17.5, P<0.001), but after propensity matching the groups did not differ (P=0.15). Patients in the microdecompression group had shorter hospital stays, both for single level decompression (difference 1.5 days, 95% confidence interval 1.7 to 2.6, P<0.001) and two level decompression (0.8 days, 1.0 to 2.2, P=0.003). Conclusion At one year the effectiveness of microdecompression is equivalent to laminectomy in the surgical treatment of central stenosis of the lumbar spine. Favourable outcomes were observed at one year in both treatment groups. Trial registration ClinicalTrials.gov NCT02006901.BMJ: British medical journal 04/2015; 350(apr01 1). DOI:10.1136/bmj.h1603 · 16.30 Impact Factor
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ABSTRACT: This study was designed to compare conventional closure with a drain and quilting suture of mastectomy dead space for preventing wound seroma. Consecutive patients undergoing mastectomy for breast cancer were included in this retrospective observational study. Patients received conventional closure with drainage or quilting suture for wound closure. Propensity score (PS) matching was performed based on potential confounders to minimize selection bias. The primary outcome was the rate of type 2 or 3 wound seroma according to the common terminology criteria for adverse events (CTCAE) definition. A total of 119 patients were included (quilting suture n = 59; conventional closure n = 60). Type 2 or 3 seroma was observed in 6.8 % of the quilting suture group and 21.7 % of the conventional closure group (crude odds ratio 0.26; 95 % confidence interval 0.08-0.86; p = 0.03). The overall seroma rate was 15.2 % in the quilting suture group and 51.7 % in the conventional closure group (p < 0.001). Persistent pain at days 15-21 was significantly less frequent in the quilting suture group than in the conventional suture group. PS matched analysis confirmed these findings, in particular the lower rate of type 2 or 3 seroma in the quilting suture group than in the conventional closure group (PS-matched odds ratio 0.16; 95 % confidence interval 0.04-0.72; p = 0.02). Quilting suture of the mastectomy dead space is associated with significantly less frequent seroma than conventional closure with drain.Annals of Surgical Oncology 03/2015; DOI:10.1245/s10434-015-4511-6 · 3.94 Impact Factor
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ABSTRACT: Conflicting reports exist regarding the role of statins in male gonadal and sexual function. Some studies report a beneficial effect, particularly for erectile dysfunction (ED), through statins' anti-inflammatory and cardiovascular protective properties. Others suggest that statins might be associated with sexual dysfunction through negative effects on hormone levels. This study aims to compare the risk of gonadal or sexual dysfunction in statin users vs. nonusers in a single-payer healthcare system. This was a retrospective cohort study of all male patients (30-85 years) enrolled in the Tricare San Antonio market. Using 79 baseline characteristics, we created a propensity score-matched cohort of statin users and nonusers. The study duration was divided into a baseline period (October 1, 2003 to September 30, 2005) to describe patient baseline characteristics, and a follow-up period (October 1, 2005 to March 1, 2012) to determine patient outcomes. Statin users were defined as those prescribed a statin for ≥3 months between October 1, 2004 and September 30, 2005. Outcomes were identified as the occurrence of benign prostatic hypertrophy (BPH), ED, infertility, testicular dysfunction, or psychosexual dysfunction during the follow-up period as identified by inpatient or outpatient International Classification of Diseases, 9th Revision, Clinical Modification codes. Logistic regression was used to determine the association of statin use with patient outcomes. Of 20,731 patients who met study criteria, we propensity score-matched 3,302 statin users with 3,302 nonusers. Statin use in men was not significantly associated with an increased or decreased risk of BPH (odds ratio [OR] 1.08; 95% confidence interval [CI] 0.97-1.19), ED (OR 1.01; 95% CI 0.90-1.13), infertility (OR 1.22; 95% CI 0.66-2.29), testicular dysfunction (OR 0.91; 95% CI 0.73-1.14), or psychosexual dysfunction (OR 1.03; 95% CI 0.94-1.14). Statin use was not associated with increased risk of being diagnosed with gonadal or sexual dysfunction in men. Further studies using a larger sample may be needed. Davis R, Reveles KR, Ali SK, Mortensen EM, Frei CR, and Mansi I. Statins and male sexual health: A retrospective cohort analysis. J Sex Med **;**:**-**. © 2014 International Society for Sexual Medicine.Journal of Sexual Medicine 11/2014; 12(1). DOI:10.1111/jsm.12745 · 3.15 Impact Factor