LETTERS TO THE EDITOR

cause of death. If foul play is suspected, an investigation will usually result. The medical certification of causes of death is designed to identify the underlying cause of death for primary mortality tabulations. In most cases, it will not provide sufficient information needed for epidemiologic studies as Salmi, et al, have found. On the other hand, it can provide a starting point for an epidemiologic investigation. By following back on a certain disease or condition, death certificates reporting (in this case, "choking on food") relevant information on the event, including causative factors, can be collected. The follow-back may be to the family of the decedent, the hospital, the attending physician, and to the corner or medical examiner in medico-legal cases. The complete reporting of relevant medical information has long been a problem affecting the quality of medical certification. Proper training is certainly needed, but payment to and evaluation in the sense of accreditation of certifiers do not seem practical or desirable. It is the obligation of the attending physician to the decedent and the family to make complete and accurate statements on the causes of death. How can you limit medical certifications to "qualified" certifiers who may not be familiar with the medical problems of the decedent? Iwao M. Moriyama, PhD Executive Director, International Institute for Vital Registration and Statistics, 9650 Rockville Pike, Bethesda, MD 20814

© 1990 American Journal of Public Health

Comments from NCHS/Rosenberg The National Center for Health Statistics (NCHS) has a number of activities, underway or planned, to address problems that Salmi, et al, have identified. One of these is encouraging states to implement a program of querying death certificates that contain incomplete or questionable information, using NCHS querying guidelines. 1,2 Querying is one of the more effective ways to improve the quality and completeness of vital records information and to educate certifying physicians about how to complete the death certificate.3.4 It should be noted that changes resulting from querying may appear only in the mortality statistical files and not as amendments to the actual death certificates. 752

Salmi, et al, call attention to the long-recognized competition between the goals of expeditious disposal of the body on the one hand and the need to obtain accurate and complete information on cause of death on the other. Their suggestion for two separate death certificates, however, is not practical. An approach to the problem is embodied in the latest revision of the US Standard Certificate of Death recommended to the states for implementation effective with deaths occurring in 1989.5 This is the provision for two physician signatures on the death certificate. With a two-signature certificate, if the attending physician is not available and the death is clearly not a medical-legal case, another physician may pronounce and certify to the time and place of death and sign the certificate so that the body can be expeditiously released to the funeral director. The funeral director then has to contact the attending physician to obtain the medical certification at a later time. Salmi's letter underscores the need for continued diligence by physicians to improve the quality of cause-of-death statistics based on information reported on death certificates. A recent workshop sponsored by NCHS and the US National Committee on Vital and Health Statistics concluded that better education of physicians in cause-ofdeath certification is important to improving the quality of data from death certificates. Such a program should encompass medical schools, internship and residence programs, and continuing education for practicing physicians. Licensure and board certification provide additional opportunities to communicate these concepts to physicians. Overall, statistical indicators of quality of the national mortality file indicate a high level of completeness.6 But, as Salmi, et al, and others have demonstrated, there is room for improvement in completing information on death certificates, which provide the basis for the nation's mortality statistics. REFERENCES 1. National Center for Health Statistics: Guidelines for Implementing Field and Query Programs for Registration of Births and Death, 1983. Instruction Manual, Part 18, Hyattsville, MD: NCHS, 1982. 2. National Center for Health Statistics: Cause of Death Querying: Instruction Manual. Part 20. Hyattsville, MD: NCHS, 1985. 3. Rosenberg HM: Improving cause-of-death statistics. Am J Public Health 1989; 79:563-564. 4. Hopkins DD, Grant-Worley JA, Bollinger TL: Survey of cause-of-death query criteria used by

state vital statistics programs in the US and the efficacy of the criteria used by the Oregon vital statistics program. Am J Public Health 1989; 79:570-574. 5. Freedman MA, Gay GA, Brockert JE, Potrzebowski PW, Rothwell CJ: The 1989 revision of the US standard certificates of live birth and death and the US standard report of fetal death. Am J Public Health 1988; 78:168-172. 6. National Center for Health Statistics: Vital Statistics of the United States, 1987, Vol. II, Mortality, Part A, Technical Appendix. DHHS Pub. No. (PHS) 90-1122. Washington, DC: Govt Printing Office, 1990.

Harry M. Rosenberg, PhD National Center for Health Statistics, 3700 EastWest Highway, Hyattsville, MD 20782

Methods Omitted to Calculate Confidence Intervals In a 1988 article by Murray and Lynch,' the authors thoughtfully provided confidence intervals for proportions. Unfortunately, they did not provide the method(s) used for calculating the confidence intervals. For confidence intervals that were presented within the text of their article, I was able to determine that the confidence intervals were calculated using the normal approximation to the binomial.2 In two of the confidence intervals presented in the text, the normal approximation was used when an exact binomial confidence interval would have been more appropriate.2 In addition, the confidence intervals reported in their Table 2 could not be duplicated using the normal approximation (with and without a correction factor3), quadratic,3 Wilson,4 Miettinen mid-P exact,4 or Fisher exact methods.2.4 In several instances the lower or upper bound of the confidence intervals provided by the authors were off more than 8 percent compared to Fisher exact binomial confidence limits calculated from the authors data. While this letter is not intended to detract from the public-health importance of the article, it would have been useful if the authors had provided the method(s) used to calculate the confidence intervals. In addition, it is surprising that the confidence intervals in their Table 2 were not calculated using one of the methods described above. REFERENCES 1. Murray DL, Lynch MA: Determination of immune status to measles, rubella, and varicellazoster viruses among medical students: assessment of historical information. Am J Public Health 1988; 78:836-838. 2. Rosner B: Fundamentals of Biostatistics. Boston: Duxbury, Press, 1982; 117-122.

AJPH June 1990, Vol. 80, No. 6

LETTERS TO THE EDITOR 3. Fleiss JL: Statistical Methods for Rates and Proportions, 2nd Ed. New York: John Wiley & Sons, 1981; 13-15. 4. Rothman KJ, Boice JD, Jr; Epidemiologic Analysis with a Programmable Calculator. NIH Pub No. 79-1649. Bethesda, MD: National Institutes of Health, 1979; 31-32.

Kevin M. Sullivan Division of Nutrition, Center for Health Promotion and Education, Centers for Disease Control, MS A08, Atlanta, GA 30333.

Dr. Murray's Response I appreciate the letter written by Mr. Sullivan concerning the article published by my colleague and me.' While our article dealt with the public health issue of medical schools using undocumented histories as proof of immunity to viral diseases such as measles, rubella, and varicella, I agree that some effort to identify the methods employed

to calculate the probability estimates used should have been included. As Mr. Sullivan correctly surmised, we used the normal approximation to the binomial.' Unfortunately, as Mr. Sullivan discovered, and I have learned, unrecognized calculation errors resulted in the publication of incorrect confidence limits for many of the values. Table 2, Probability Estimates of Undocumented Historical Information, has now been revised using the correct normal approximation to the binomial for the majority of the confidence limits. For those instances in Table 2 when np(l - p) c 5 (where n = sample size and p = the proportion with the outcome), such as occurred with the Measles ELISA calculations, published tables2.3 were used to develop the confidence limits. As senior author and principal in-

vestigator on this project, I sincerely regret the errors made on Table 2 in our original publication, and thank Mr. Sullivan for his interest. REFERENCES

1. Rosner B: Fundamentals of Biostatistics. Boston: Duxbury Press, 1982. 2. Hald A: Statistical Tables and Formulas. New York: John Wiley and Sons, 1952. 3. Rao C, Mitra S, Matthai A: Formulae and Tables for Statistical Work. Calcutta: Statistical Publishing Society, 1966. Dennis L. Murray, MD Associate Professor, Department of Pediatrics and Human Development, B240 Life Sciences, Michigan State University, East Lansing, MI 482241317. Editor's Note: The only notable correction in Dr. Murray's table is the sensitivity of Measles IAHA Disease, which should be 63.7 percent instead of 67.3 percent as published (AJPH 1988; 78:837, Table 2). The complete corrected table may be requested from Dr. Murray at the address above. The Journal staff regrets the delay in publishing this exchange.

Call for Abstracts APHA 'Late-Breaker' Epidemiology Exchange Session The Epidemiology Section will sponsor a "Late-Breaker" Epidemiology Exchange on Wednesday, Oct. 3, 1990, 2:00-5:00 pm, at APHA's 118th Annual Meeting to be held in New York City, Sept. 30-Oct. 4. The Exchange will provide a forum for presentation of investigations, studies, methods, etc., which have been conceived, conducted, and/or concluded so recently that abstracts could not meet the deadline for submission to other Epidemiology Sessions. Papers submitted should report on work conducted during the last 6-12 months. Abstracts should be limited to 200 words; no special form is required. Abstracts should be submitted to Robert A. Gunn, MD, Division of Field Services, Epidemiology Program Office, Building 11 South, Mailstop F-15, Centers for Disease Control, Atlanta, GA 30333-Telephone: 404/639-0336; FAX 404/639-0277, and must be received by August 13, 1990. Receipt of abstract will be acknowledged by postcard and acceptance will be decided by August 17, 1990.

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Methods omitted to calculate confidence intervals.

LETTERS TO THE EDITOR cause of death. If foul play is suspected, an investigation will usually result. The medical certification of causes of death i...
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