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Relationship between a uterine fibroid diagnosis and the risk of adverse obstetrical outcomes: a cohort study
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  • Published on:
    Response to the comments
    • Kamilla Karlsen, MD, PhD University of Southern Denmark
    • Other Contributors:
      • Ulrik Kesmodel, Professor
      • Pernille Ravn, professor

    We thank Dr. Elizabeth A Pritts, Dr. David L Olive, and Dr. William H. Parker for their great interest in our study and for the very qualified comments. To investigate the influence of uterine fibroids on obstetrical outcomes is complex and can be viewed from different angles. - We aimed to investigate symptomatic uterine fibroids. Well conducted cohort studies are the best available substitutes when experiments are not possible. Methodological limitations need to be taken into consideration, and associations can be explored. We are fully aware that limitations must be relevantly discussed. David A Grimes 1 pointed out some important issues regarding cohort studies:
    1) The exposure should be clear: we argue to have a clearly defined exposure.
    2) The importance of potential confounders: we have been able to include important confounders using the directed acyclic graph, DAG.
    3) Awareness that the risk of a weak association (HR 0.5-2) is likely to be due to bias and not causation: We have clearly stated that we have found associations and further that the association could be interesting for further research, but we do not recommend changes in clinical recommendations.
    The risks of misclassification of exposure were related to the uterine fibroid diagnoses codes. The daily clinical coding may be incorrect or lacking due to various work-related distractions or variable individual interpretation of clinical cases. The low prevalence of uterine fibroids...

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    Conflict of Interest:
    None declared.
  • Published on:
    Fibroids and Obstetrical Outcomes

    To the Editor,

    I read with interest the article by Karlsen, et al. concluding that here was an association between clinically significant uterine fibroids and pre-term birth. (1) The study has several significant shortcomings. The likely inaccuracies of the use of a large retrospective, administrative, coded database and the low prevalence of fibroids only identified clinically and not confirmed by ultrasound or other imaging modality were mentioned by the authors in the limitations section of the article. However, the degree of these limitations makes the data uninterpretable and the conclusions unfounded.

    Administrative databases are inadequate to answer clinical questions as they are subject to clinical misdiagnosis and coding errors which are blind to the goals of the study. The only way to assure accuracy of such a data set is to adjudicate the data by chart review, which was not done by the authors.

    Reliance on clinical examination to determine the presence of uterine fibroids, especially submucous fibroids that might more significantly impact pregnancy, is inaccurate. (3) Virtually all women in the developed world currently have an ultrasound as part of their early pregnancy evaluation. Most studies using ultrasound for the diagnosis of fibroids in early pregnancy report a prevalence of 3-4%. One such study found that among 64,047 pregnant women, 2058 had fibroids diagnosed with 1st trimester US, a prevalence of 3.2%. (Stout)

    The c...

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    Conflict of Interest:
    None declared.
  • Published on:
    Dear Dr. Karlsen and Colleauges,
    • Elizabeth A Pritts, Reproductive Endocrinologist Wisconsin Fertility Institute
    • Other Contributors:
      • David L Olive, Reproductive Endocrinologist

    We read Dr. Karlsen’s paper entitled “Relationship between a uterine fibroid diagnosis and the risk of adverse obstetrical outcomes: a cohort study” with great interest. We understand the authors evaluated a large and complicated set of data and appreciate their effort. However, the authors used a database fraught with errors without validation of said database, made incorrect assumptions and conclusions about the data, and incompletely discussed some of the major queries in the discussion.

    The first issue surrounds the use of the Danish National Birth Cohort, Patient Registry and Birth Registry. Although the authors write about the limitations of a registry that uses codes “more closely connected to hospital budgets than hospital diagnosis codes”, they rely on a single study to prove the quality of their database.

    Multiple authors have shown that administrative databases are inadequate to answer clinical questions. They are are set up for billing purposes only, not epidemiological research (1,2), and elaborate statistical machinations do not overcome the impact of anomalous data (3). Several studies have shown that the very registry used in this report; the Danish National Patient Registry, is highly inaccurate from a clinical standpoint. The authors from a study in 2009 have a self-proclaimed 10% inaccuracy rate in their diagnoses addressing oral contraceptive research (4). Other authors have found higher erroneous rates for diagnoses of hypertension, rhe...

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    Conflict of Interest:
    None declared.