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NEW YORK (Reuters Health) - Older adults who have a colonoscopy performed by a family doctor, internist or general surgeon are somewhat more likely to need another one within a year compared with those who have the procedure done by a gastroenterologist, a new report finds.The study, based on Medicare data for more than 300,000 colonoscopy procedures, found that 5 percent of patients had a repeat colonoscopy within a year. Of 7,700 colonoscopies done by a family physician, 6.4 percent were followed up with a repeat procedure within the year. The corresponding figures were 5.6 percent for general surgeons and 5.3 percent for internists. Of the roughly 240,000 colonoscopies performed by a gastroenterologist -- doctors who specialize in the digestive system -- 4.6 percent were followed by a repeat procedure within a year.After factoring in variables like patients' ages, other medical problems and income levels, the researchers found that having a colonoscopy done by a family physician was associated with a 39 percent greater chance of needing a repeat procedure, versus having one done by a gastroenterologist.Those figures were 18 percent and 12 percent, respectively, when the initial colonoscopy was performed by a general surgeon or internist. There are instances where such "early" repeat colonoscopies are warranted, the authors emphasize in their report in the American Journal of Gastroenterology. For example, people who are found to have large, difficult-to-remove polyps -- growths in the colon that can develop into cancer -- may need to have a follow-up procedure within a few months. Most people can wait at least several years before their next colonoscopy, however, and an early repeat procedure can be a sign of shortcomings in the quality of the first one, the researchers say. Because the current study is based on Medicare claims data, it is not possible to know why family doctors, internists and general surgeons had higher rates of repeat colonoscopies, said lead researcher Dr. Cynthia Ko, an assistant professor of gastroenterology at the University of Washington in Seattle.But, she told Reuters Health in an e-mail, "it is certainly possible that non-gastroenterologists have less experience with the procedure, and that may be one reason for the more frequent repeat exams."That does not mean that any individual family physician, internist or general surgeon lacks experience in colonoscopy, and asking doctors about their personal experience is always a good idea, Ko noted."I think it is useful for patients to ask any physician -- gastroenterologist or non-gastroenterologist -- how much experience they have with the procedure, and how many they have done," she said.There is no firm number signifying that a doctor has performed "enough" colonoscopies, according to Ko. But she noted that studies of trainees, such as gastroenterology fellows, have suggested that doctors need to perform about 500 colonoscopies before they are able to consistently reach the cecum -- the area at the top of the colon -- and make the colonoscopy complete.The findings are based on Medicare claims for 328,167 outpatient colonoscopies performed on adults age 66 and older -- for either colon cancer screening or diagnosis. Most of the procedures, 73 percent, were performed by a gastroenterologist.General surgeons performed 13 percent, internists about 5 percent, and family physicians just over 2 percent. Colorectal surgeons and "other" specialists accounted for the rest. Ko's team found that besides doctors' specialty, the setting of the colonoscopy affected the odds of an early repeat procedure. Six percent of office-based colonoscopies were followed by an early repeat procedure, compared with 5 percent of hospital-based ones, and about 4 percent of those done at an ambulatory surgery center. When the researchers weighed other factors, the likelihood of an early repeat colonoscopy was 27 percent higher when the original procedure was done in a doctor's office rather than a hospital.Again, Ko said, the reason for the difference is not known. But she noted that there are more-strict credentialing requirements for colonoscopy services provided at hospitals and ambulatory surgery centers compared with medical offices.And in an earlier analysis of this same study group, Ko's team found that rates of polyp detection and removal tend to be higher with hospital-based exams versus office-based ones -- suggesting, she said, that the hospital procedures might be higher quality.The American Academy of Family Physicians (AAFP), which represents about 95,000 family doctors in the U.S., declined to comment directly on the findings. But a spokesman pointed to the organization's position paper on colonoscopies, available on the group's Web site. It states that "family physicians are trained to diagnose, treat, manage and appropriately refer patients with gastrointestinal disorders." The document also says studies indicate that family physicians who perform colonoscopies "compare favorably" with gastroenterologists and general surgeons when technical competency is measured by factors like complication rates, time needed to perform the procedure and the likelihood of reaching the cecum during the exam. In addition, AAFP asserts there are potential advantages to having family physicians perform colonoscopies -- including lower costs to patients, less "fragmentation" in individual patients' care, and having a doctor you "know and trust" perform the procedure.People in rural areas, who may have to travel far for specialist care, may particularly benefit, the group says.