A National Survey of Primary Care Physicians' Methods for Screening for Fecal Occult Blood

Context Authorities recommend at-home fecal occult blood tests (FOBTs), using 2 samples from 3 consecutive bowel movements, as one of several options for colorectal cancer screening. Content The authors asked a national sample of 1147 primary care physicians about their colorectal cancer screening practices. Approximately 33% reported using only a single in-office stool sample for FOBT. To follow up positive results, approximately 30% said that they repeated the FOBT, and about the same percentage recommended sigmoidoscopy rather than total colon examination. Implications Many primary care physicians in the United States may use inadequate methods to screen for colorectal cancer. The Editors The fecal occult blood test (FOBT) is the least expensive and simplest of the tests recommended in national guidelines for colorectal cancer screening (1-6). Nevertheless, implementation requires several decisions that determine the effectiveness of screening. These include the brand of FOBT to use, whether to give patients the multiple-specimen home kit or to conduct in-office FOBT with a single specimen obtained during a digital rectal examination, and selection of a follow-up test for patients with positive results (7). While randomized, controlled trials have shown that FOBT reduces colorectal cancer incidence and mortality (8-13), the effectiveness and cost-effectiveness of FOBT screening in general clinical practice depend on the degree to which health professionals follow recommended testing guidelines. National colorectal cancer screening and clinical practice guidelines (1-6, 14) recommend performing FOBT screening with the home test, the method used in the randomized, controlled trials. To our knowledge, no studies have examined the efficacy of in-office FOBT, and a recent study showed that the in-office test is substantially less sensitive than the home test (15). Patients with positive results on FOBT should have an examination of the entire colon and rectum (2-7). Repeating FOBT before diagnostic work-up to increase test specificity is not recommended because of the significant probability of finding colorectal cancer or a large adenoma among patients with a positive test result (7). We report on the practice of FOBT in the United States as ascertained in the national Survey of Colorectal Cancer Screening Practices (SCCSP) in Health Care Organizations. This survey asked primary care physicians about how they used FOBT in their practices (16). To determine whether physician responses were consistent with those of the public, we also examined data from the nationally representative sample of the U.S. population that completed the 2000 National Health Interview Survey (NHIS) (17). Methods Survey of Colorectal Cancer Screening Practices The National Cancer Institute conducted the SCCSP in collaboration with the Centers for Disease Control and Prevention and the Centers for Medicare & Medicaid Services. The researchers used the American Medical Association's Physician Masterfile to form a nationally representative sample of primary care physicians, including general practitioners, family practitioners, general internists, and obstetriciansgynecologists. The survey took place between November 1999 and April 2000. Eligible respondents were physicians 75 years of age or younger who had an active license to practice medicine and whose major professional activity was patient care. Physicians who were retired; in residency training; or involved in full-time teaching, research, or administration were excluded. Obstetriciansgynecologists were included in the sample because they provide preventive services for many women in the United States (18). Respondents were offered a choice of response modes (mail, fax, telephone, or secure Internet Web site). Ninety percent responded by mail. Additional details of the sampling and survey methods have been described elsewhere (16). Physicians were asked how many times they ordered or performed colorectal cancer screening with FOBT for asymptomatic average-risk patients. Respondents who ordered or performed FOBT at least once during a typical month were also asked the brand of test they used, whether they used in-office FOBT, home FOBT, or both (Complete a single FOBT card in the office during a digital rectal exam, Give or mail patients a set of three FOBT cards to complete at home, Both of the above, or Other [describe]) for most of their patients, and whether they had a mechanism to ensure that patients who were given or mailed home FOBT kits completed and returned them. Physicians were asked which procedure or procedures they usually recommended to healthy, average-risk patients as an initial follow-up test after positive results on FOBT: repeated FOBT, flexible sigmoidoscopy, colonoscopy, double-contrast barium enema (DCBE), or other (describe). Respondents were allowed to check more than 1 procedure, indicated in this report by test a/test b (for example, sigmoidoscopy/colonoscopy). We analyzed follow-up of positive FOBT results in 2 steps (Figure). Among the 1120 physicians who performed FOBT at least once per month and responded to the follow-up question, we looked first at whether they recommended repeating the FOBT. We then examined which tests were recommended for the diagnostic work-up. At this second step, we did not include respondents who only reported recommending repeated FOBT (n= 151) and those who only indicated that they referred patients to another physician (specialist or primary care) for follow-up of positive FOBT results (n= 44). Figure. Two-step analysis of follow-up of positive results on fecal occult blood tests ( FOBTs ). The American Cancer Society and the GI Consortium have provided explicit guidelines on method of specimen collection and follow-up of positive test results (2, 3). We considered physicians to be influenced by guidelines if they responded that at least 1 of these guidelines was very influential in their screening recommendations. Respondents were also asked to comment on the capacity to perform colonoscopy in their geographic practice area and whether, in the past 3 years, they had completed continuing medical education courses on colorectal cancer screening. NHIS The NHIS, conducted by the Centers for Disease Control and Prevention's National Center for Health Statistics, is an in-person survey that collects health behavior and sociodemographic information from the civilian, noninstitutionalized U.S. population by using multistage sampling. The 2000 NHIS Cancer Control Module included questions on the use of cancer screening. The final response rate for the module was 72% (17). A total of 11365 men and women 50 years of age or older responded to questions about FOBT use. Respondents were asked whether they had ever had a blood stool test using a home test kit, the time since their last test, and whether they had ever had a home blood stool test with abnormal results. Those responding affirmatively were asked what additional tests or surgery they had because of these results. After the series of questions related to home FOBT, respondents were asked if they had ever had an in-office test and how much time had passed since their last test. Respondents were not asked about abnormal results on in-office tests. Statistical Analysis We conducted univariate and multivariate analyses of data from the SCCSP. For the univariate analysis, we estimated percentages and confidence intervals for each level of an explanatory variable. We performed a Pearson chi-square test to test the association between each explanatory variable and the response variable for Tables 1 and 2. For the multivariate analysis, we used logistic regression and computation of predictive margins to estimate the probability of each outcome variable when we controlled for all other independent variables in Tables 1, 2, and 3. These adjusted percentages (that is, predictive margins) are a type of direct standardization that averages the predicted values from the logistic regression models over the covariate distribution in the population (19). These adjusted percentages do not reflect actual use in the population but allow comparisons across categories of the variables included in the models. They are easier to interpret than odds ratios and do not require designating one of the groups as the referent group. Table 1. Percentage of Physicians Who Use In-Office Fecal Occult Blood Tests Table 2. Percentage of Physicians Who Repeat Fecal Occult Blood Tests after Abnormal Results Table 3. Percentage of Physicians Who Recommend Alternative Diagnostic Work-up after Positive Results on Fecal Occult Blood Tests We did a Wald chi-square test to test the association between each explanatory variable and the response variable while adjusting for all other variables in the table. To permit generalization of the results of both the univariate and multivariate analyses to the U.S. population of practicing primary care physicians, we used sampling weights to account for the probability of selection and nonresponse. We used the SAS statistical package, version 9.0 (SAS Institute, Inc., Cary, North Carolina) (20), and SUDAAN, version 8.0. 2 (Research Triangle Institute, Research Triangle Park, North Carolina) (21), to compute prevalence rates, predictive margins, confidence intervals, and P values. We conducted univariate analyses of the NHIS data, using SUDAAN to compute point estimates and confidence intervals to account for the complex survey design (17). Role of the Funding Sources The funding sources, the National Cancer Institute and the Centers for Disease Control and Prevention, had a role in the design, conduct, and reporting of the study. Results Survey of Colorectal Cancer Screening Practices Description of Respondents Of the 1718 eligible physicians, 1235 responded to the survey (overall response rate, 72%). Personal and practice characteristics of these respondents have been described el