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Appendix D Questions and Methods in Surveillance Programs
Pages 327-346

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From page 327...
... CHARACTERISTICS OF INTEREST Probabilities of Outcome Events An analysis of adverse device events should distinguish between events that are clearly identifiable as being due to a device (e.g., fracture of a cochlear implant) and those that can occur in individuals with the same disease or condition whether or not they have the device (e.g., development of meningitis in someone with a cochlear implant)
From page 328...
... 328 SAFE MEDICAL DEVICES FOR CHILDREN adverse event reports would also allow one to identify characteristics of a device user (e.g., gender, age, or disease severity) that might affect the probability of an adverse event.1 Quantitatively, for adverse events (AE)
From page 329...
... APPENDIX D 329 than (less than) 1 indicates that use of the device is associated with a higher (lower)
From page 330...
... , but no agency procedures, incentives, or other mechanisms exist to ensure that such reporting occurs. Even with perfect reporting, that system would not include denominator data, although such data might be collected or estimated in certain cases (e.g., if a manufacturer could provide reasonably complete information on patients implanted with a particular kind of device or if data from other sources allows reasonable estimates of the number of people with the relevant medical condition)
From page 331...
... Sometimes, however, information is being actively collected on people with a medical device but not on people without a device, so that both the number and characteristics of this group are unknown. SPECIFIC STUDY DESIGNS AND INFORMATION RESOURCES This section discusses several specific strategies for evaluating the safety and effectiveness of medical devices.
From page 332...
... 332 SAFE MEDICAL DEVICES FOR CHILDREN Randomized Controlled Trials and Other Interventional Studies Randomized comparative clinical trials, typically called Phase III trials in the world of pharmaceutical studies, are considered to be the most reliable scientific design for evaluating the safety and efficacy of an intervention. Ideally, a random sample of subjects is selected from a well-defined target population, and then subjects are randomly assigned to one of several interventions.
From page 333...
... In the 1980s, such a design was used to assess the efficacy of therapy involving extracorporeal membrane oxygenation (ECMO, also called extracorporeal life support or ECLS) , a form of cardiopulmonary life support that involves an array of medical devices (e.g., vascular access catheters, blood pump, tubing, an artificial lung [often called an oxygenator]
From page 334...
... 334 SAFE MEDICAL DEVICES FOR CHILDREN supported the findings of the first trial. Because adaptive designs have the potential of assigning more subjects to the better intervention arm, they provide an attractive alternative in some settings.
From page 335...
... APPENDIX D 335 sions. A likely recent example is the Women's Health Initiative, which demonstrated an increased risk of certain cardiovascular outcomes among women receiving estrogen therapy, when previous observational studies showed no evidence of increased risk, and in some cases a protective effect (Manson et al., 2003)
From page 336...
... 336 SAFE MEDICAL DEVICES FOR CHILDREN types of events, such as a diagnosis of cardiomyopathy, are routinely maintained, for then a relatively large number of cases can be readily obtained and matched with controls to identify possible risk factors for the outcome. Also, event reporting systems, such as the MedSun system currently being implemented by the FDA, lend themselves to case-control studies to identify possible safety concerns with devices, provided that there is a means of selecting controls to match the cases and to ascertain the "exposure" status (e.g., device use or not)
From page 337...
... APPENDIX D 337 event databases. The risk of a particular adverse event (AE1)
From page 338...
... 338 SAFE MEDICAL DEVICES FOR CHILDREN forced to fall back on anecdotal evidence and the analyses of databases of spontaneous reports. The FDA, device manufacturers, and some other organizations maintain voluminous databases of spontaneously reported adverse events, consisting of coded and uncoded text descriptions of the patient, the device, what happened to the device, and what the effect of the adverse event was on the patient.
From page 339...
... APPENDIX D 339 the letter n to denote and emphasize the count in the first cell, where both the drug and the adverse event are present. The disproportionality measures are all of the form n/e, where e is a baseline or comparator value that is expected to be near n if the drug and the adverse event are not associated.
From page 340...
... 340 SAFE MEDICAL DEVICES FOR CHILDREN receive a high proportion of vaccines. If the database is restricted to reports involving infants, the associations disappear.
From page 341...
... APPENDIX D 341 gamma-Poisson shrinker" (MGPS) is described in DuMouchel (1999)
From page 342...
... 342 SAFE MEDICAL DEVICES FOR CHILDREN associations in the database is called feature extraction. But the feature extraction step introduces another layer of uncertainty into the analysis, and is usually less informative than being able to work with adverse event codes that fit a well structured theoretical framework.
From page 343...
... APPENDIX D 343 TABLE D.1 List of 12 Shunt Complication Event Types and the Text Strings That Were Used to Classify the Reports in Searching the Descriptive Narrative in MAUDE Reports Abdominal Cyst "peritonitis," "pseudocyst," "pseudo-cyst," ("cyst" & "abdom") , ("cyst" & "periton")
From page 344...
... 344 SAFE MEDICAL DEVICES FOR CHILDREN TABLE D.3 The 15 Largest Reporting Ratios (RR = N/E) for Manufacturer­Event Type Combinations Listed in Table D.1 Manufacturer Code Event N E RR EBGM 1 Man.
From page 345...
... APPENDIX D 345 values of N and E than any other combination in Table D.3, actually has the largest "true" relative reporting ratio, EBGM = 1.85. A reporting ratio of 1.85 is interpreted as an estimated 85 percent excess frequency in disconnection reports for manufacturer D compared to the number expected if there were no association between manufacturer and shunt complication event type in the database.
From page 346...
... 346 SAFE MEDICAL DEVICES FOR CHILDREN O'Neill RT, Szarfman A


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