Chen et al. Respond to "Studying the Epidemiology of Uterine Leiomyomata" by Schwartz

Chao-Ru Chen1, Germaine M. Buck1, Jean Wactawski-Wende1,2 and Kimberly M. Perez1

1 Department of Social and Preventive Medicine, School of Medicine and Biomedical Sciences, University at Buffalo, State of New York, Buffalo, NY.
2 Department of Gynecology-Obstetrics, School of Medicine and Biomedical Sciences, University at Buffalo, State of New York, Buffalo, NY.


    INTRODUCTION
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 INTRODUCTION
 REFERENCES
 
We thank Dr. Schwartz for reviewing the methodological issues underlying the epidemiologic study of uterine leiomyomas, or fibroids (1Go). We concur with him about the paucity of available research despite the prevalent nature of this gynecologic condition. We would like to respond to the concerns raised by Dr. Schwartz regarding our case ascertainment and choice of analytical strategy, both of which impacted on our interpretations.

Dr. Schwartz discussed two factors that may have resulted in underascertainment of cases in our study: use of laparoscopy and the lack of a protocol for laparoscopic detection of fibroids. As we noted in the description of our methodology (2Go), this study was originally designed to assess the safety and efficacy of tubal ligation. Hence, women were not undergoing laparoscopic screening for asymptomatic disease per se. We agree that there may have been misclassification of controls due to the inability of laparoscopy to detect fibroids within the myometrium or endometrium. Fibroids located at these sites may be associated with heavier bleeding, thereby increasing the likelihood of clinical recognition and diagnosis. We are unaware of population-based data delineating fibroids with respect to size, location, or symptomology which would enable us to better characterize the extent of underascertainment of cases in our sample and the implications for study findings. Concerning the absence of a protocol for the detection of fibroids in our study, it should be noted that surgeons were instructed to systematically record any and all gynecologic pathology visualized at the time of sterilization.

We agree that there is a dearth of available information on racial differences and fibroids, but our study is not the first to have addressed race (3GoGo–5Go). This dearth of attention to race served as an impetus for us to assess risk factors for White and Black women separately, with the implicit intention of stimulating further hypothesis-driven research. The backward elimination approach is well-suited to this purpose (6Go). The limited number of Black women available for study impacted on our statistical power; hence, we focused on factors that achieved statistical significance.

We agree that the inclusion of cases with a history of fibroids (n = 121) along with newly diagnosed cases (n = 196) may be problematic, especially with respect to the temporal ordering between exposures and disease status. Our original paper included only women who were diagnosed with fibroids at tubal sterilization, but we reluctantly conceded to a reviewer's request for the inclusion of all cases. Still, we recognize the implications of our case definition for the interpretation of results, as noted in our Discussion (2Go).

The use of this select sample—fertile women of reproductive age undergoing laparoscopy for tubal sterilization—afforded us a unique opportunity to assess fibroids in relation to alleged risk factors. We can estimate prevalence by case definition (prior history, visualization, or both) for fertile women. Many existing studies comprise clinical samples of women with symptomatic fibroids or other gynecologic complaints such as infertility or dysfunctional bleeding. Our cohort included younger women whose fibroids may have been in the formative stages of development. Epidemiologists continue to face the challenge of identifying risk factors and at-risk subgroups in the elucidation of etiologic mechanisms. Challenges facing epidemiologic inquiry can be overcome by utilizing technologies better suited for more complete case ascertainment. Still, the issue of when and whom to screen remains speculative; but it should not impede successful design and implementation of prospective inquiry. We agree that uterine leiomyoma must continue to be a high research priority.


    NOTES
 
Reprint requests to Dr. Jean Wactawski-Wende, Department of Social and Preventive Medicine, School of Medicine and Biomedical Sciences, 270 Farber Hall, University at Buffalo, State of New York, Buffalo, NY 14214 (e-mail: jww{at}buffalo.edu).


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 INTRODUCTION
 REFERENCES
 

  1. Schwartz SM. Invited commentary: studying the epidemiology of uterine leiomyomata—past, present, and future. Am J Epiderniol 2001;153:27–9.[Abstract/Free Full Text]
  2. Chen C-R, Buck GM, Courey NG, et al. Risk factors for uterine fibroids among women undergoing tubal sterilization. Am J Epidemiol 2001;153:20–6.[Abstract/Free Full Text]
  3. Baird DD, Schectman JM, Dixon D, et al. African Americans at higher risk than whites for uterine fibroids: ultrasound evidence. (Abstract). Am J Epiderniol 1998;147(suppl):S90.
  4. Kjerulff KH, Langenberg P, Seidman JD, et al. Uterine leiomyomas: racial differences in severity, symptoms and age at diagnosis. J Reprod Med 1996;41:483–90.[ISI][Medline]
  5. Marshall LM, Spiegelman D, Barbieri RL, et al. Variation in the incidence of uterine leiomyoma among premenopausal women by age and race. Obstet Gynecol 1997;90:967–73.[Abstract/Free Full Text]
  6. Kleinbaum DG. Logistic regression: a self-learning text. New York, NY: Springer-Verlag New York, 1996.
Received for publication August 29, 2001. Accepted for publication September 6, 2001.


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