title: A self-assessment efficacy tool for spermicide contraceptive users.
abstract: BACKGROUND
  Easily accessible contraceptive methods, such as chemical and barrier methods, are used currently by approximately 1 in 6 women who use contraception in the United States. Even in the face of suboptimal effectiveness, coitally dependent methods likely will always have a role in fertility management. Because most contraceptive efficacy stratifications use population-based data, for women to make informed decisions about the individual fit of a contraceptive method, better evidence-based, user-friendly tools are needed.
  
  
  OBJECTIVE
  Spermicides are a readily available, over-the counter, woman-controlled contraceptive method, but their effectiveness is user-dependent. Patient-decision aids for spermicides and other barrier methods are not well-developed, and overall failure rates could be improved by aids that account for individual characteristics. We sought to derive a prediction rule for successful use of spermicides for pregnancy prevention and to convert those data to a point-of-care instrument that women can use when they are considering spermicide use during contraceptive decision-making.
  
  
  METHODS
  We pooled local data from 3 randomized clinical trials that were published in 2004, 2007, and 2010 that tested spermicide efficacy. We constructed a prediction rule for unintended pregnancy using bootstrap validation and developed a scoring system.
  
  
  RESULTS
  Data from 621 women showed a mean age of 29 years; 49% of the women were African American, and 43% were white. The overall pregnancy rate was 10.3% (95% confidence interval, 7.9-12.7) over 6 months. In adjusted logistic regression, age >35 years was protective against pregnancy (odds ratio, 0.19; 95% confidence interval, 0.06-0.58; P = .003), and multigravidity was associated with high failure rates (odds ratio, 7.24; 95% confidence interval, 3.04-17.3; P < .001). These risk factors (together with frequency of unprotected sex) were used in a model that maximized sensitivity for pregnancy prediction to compute the predicted probability of unintended pregnancy for each woman. This model was 97% accurate in predicting women who had a <5% pregnancy risk while using spermicides.
  
  
  CONCLUSIONS
  Using prospectively collected data, we built a simple risk calculator for contraceptive failure that women can consult when considering spermicide use. This instrument could support patient-centered contraceptive decision-making.
authors.affiliation: Penn Family Planning and Pregnancy Loss Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Electronic address: schreibe@upenn.edu.
authors.forename: Courtney A
authors.initials: CA
authors.lastname: Schreiber
authors.affiliation: Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Ratcliffe
authors.affiliation: Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Mary Dupuis
authors.initials: MD
authors.lastname: Sammel
authors.affiliation: Penn Family Planning and Pregnancy Loss Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA; Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Whittaker
mesh_terms: D000328:Adult; D001741:Black or African American; D000367:Age Factors; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D016015:Logistic Models; D016017:Odds Ratio; D018802:Patient-Centered Care; D019095:Point-of-Care Systems; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D018570:Risk Assessment; D013089:Spermatocidal Agents / Q000627:therapeutic use*; D016896:Treatment Outcome; D044465:White People; D055815:Young Adult
chemical_list: D013089:Spermatocidal Agents
keywords: contraceptive efficacy; decision; spermicide; tool