(Stroke. 2001;32:1694.)
© 2001 American Heart Association, Inc.
Letters to the Editor |
Re: Stroke and Pregnancy
Veterans Affairs Medical Center, Great Lakes Health Care System, Tomah, Wisconsin
To the Editor:
Jaigobin and Silver1 performed a retrospective analysis of stroke during pregnancy or the puerperium among women who delivered at a single tertiary referral hospital in Canada over a 17-year period. The frequency of all strokes was 26 per 100 000, when corrected to represent the catchment area (ie, by excluding referred patients). This value is similar to that reported in several large studies using administrative data from the United States,2 3 4 as well as other population-based epidemiological studies in which clinical records were reviewed.5 6 7 8 The study by Jaigobin and Silver provides interesting clinical information about such patients, but several issues warrant clarification or elaboration.
First, the authors identified potential cases as those with both stroke and pregnancy diagnostic codes, as well as by review of pregnant patients with procedure codes for CT, MRI, or cerebral angiography. The "stroke codes" reportedly used for screening potential cases were 430 to 439, using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). However, there is no ICD-9-CM 439 code for stroke in the US version of this classification system.9 Furthermore, codes for cerebrovascular disease (ie, ICD-9-CM 430 to 438) in the US version specifically exclude "any condition classifiable to 430 to 434, 436, 437 occurring during pregnancy, childbirth, or the puerperium, or specified as puerperal (674.0)."9 These cases should properly be coded to ICD-9-CM 674.0, while cerebral venous thrombosis or thrombosis of intracranial venous sinuses as a complication of pregnancy or the puerperium should be coded to 671.5.9 In studies using US administrative hospital data from the National Hospital Discharge Survey or the Healthcare Cost and Utilization Project, some patients with pregnancy codes also had non-pregnancy-related stroke codes (ie, 430 to 434, 436 to 437), generally in addition to codes 674.0 or 671.5, but most cases of stroke during pregnancy or puerperium were coded only with codes 674.0 or 671.5 (Lanska and Kryscio, unpublished observations, 1997 to 1999). Did Jaigobin and Silver review these codes as well? If so, what was the relationship between codes 430 to 438 and codes 674.0 and 671.5 in these cases?
Second, the authors identified 51 potential cases by ICD-9-CM codes, only 34 of which were felt to have had a stroke after review of the medical records. What were the other diagnoses in the patients who did not have a stroke? What were the ICD-9-CM codes used in these patients? How many were identified by some stroke diagnosis code, and how many were identified by a diagnostic test procedure code?
Third, the study spanned a long period, from 1980 to 1997. Was ICD-9-CM in use in Canada during this entire period? Were there changes in the frequency of pregnancy-related stroke over this period?
Fourth, did any of the cases receive bromocriptine for lactation suppression? Postpartum lactation suppression was removed as an indication for the use of bromocriptine in 1994 in the United States. Was bromocriptine used for this indication during the entire study period in Canada? If not, was there any change in the frequency of stroke before and after removal of postpartum lactation suppression as an indication for the use of bromocriptine? Did any of the cases receive other ergot derivatives, phenylpropanolamine, or other drugs purported to be associated with stroke?
References
1.
Jaigobin
C, Silver FL. Stroke and pregnancy.
Stroke. 2000;31:2948–2951.
2. Lanska DJ, Kryscio RJ. Peripartum stroke and intracranial venous thrombosis in the National Hospital Discharge Survey. Obstet Gynecol. 1997;89:413–418.[Medline] [Order article via Infotrieve]
3.
Lanska DJ, Kryscio
RJ. Stroke and intracranial venous thrombosis during pregnancy and
puerperium. Neurology. 1998;51:1622–1628.
4.
Lanska DJ, Kryscio
RJ. Risk factors for peripartum and postpartum stroke and intracranial
venous thrombosis. Stroke. 2000;31:1274–1282.
5.
Wiebers DO,
Whisnant JP. The incidence of stroke among pregnant women in Rochester,
Minn, 1955 through 1979. JAMA. 1985;254:3055–3057.
6. Simolke GA, Cox SM, Cunningham FG. Cerebrovascular accidents complicating pregnancy and puerperium. Obstet Gynecol. 1991;78:37–42.[Medline] [Order article via Infotrieve]
7.
Kittner SJ, Stern
BJ, Feeser BR, Hebel JR, Nagey DA, Buchholz DW, Earley CJ, Johnson CJ,
Macko RF, Sloan MA, Wityk RJ, Wozniak MA. Pregnancy and the risk of
stroke. N Engl J Med. 1996;335:768–774.
8. Witlin AG, Friedman SA, Egerman RS, Frangieh AY, Sibai BM. Cerebrovascular disorders complicating pregnancy: beyond eclampsia. Am J Obstet Gynecol. 1997;176:1139–1148.[Medline] [Order article via Infotrieve]
9. US Department of Health and Human Services. International Classification of Diseases, 9th Revision, Clinical Modification: ICD-9-CM. 3rd ed. Vol 1. Washington, DC: US Government Printing Office; 1989. DHHS publication PHS 89-1260.
Response
Toronto General Hospital, Toronto, Canada
We thank Dr Lanska for his interest in our recent article and would like to clarify the following issues raised in his letter.
First, we selected the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 430 to 439 linked with pregnancy codes V22 and V23 identify patients with stroke associated with pregnancy. Although code 674.0 was considered, this identified a small proportion of patients in our cohort. The search strategy used was selected because it allowed us to identify pregnant or puerperal patients with stroke codes as a primary or secondary diagnosis. We agree that code 439 codes for the late effects of stroke. However, because of previous reports of the inaccuracy of hospital discharge coding for stroke,R1 R2 we included all stroke-related codes in our study design to avoid excluding any possible patients with stroke-associated with pregnancy.
Second, although 51 potential cases were identified, only 34 had a diagnosis of stroke after review of the medical records. The nonstroke diagnoses consisted of the following: epilepsy,R3 prior neurological deficit,R3 embolization for epistaxis, subglottic stenosis, Bell’s palsy, cerebral abscess, delirium, ovarian cyst, neurogenic bladder, neoplasm, and multiple sclerosis. An additional 2 patients had nonspecific neurological symptoms with no clinical or radiographic evidence of stroke. All patients with nonstroke diagnoses were identified by a diagnostic test procedure code.
Third, between 1980 to 1985, discharge diagnoses were translated into ICD-9 codes. After 1985, ICD-9-CM classification was used. We regret this error.
Finally, to the best of our knowledge, none of the patients with stroke during the postpartum period received bromocriptine for lactation suppression or any other medications purported to be associated with stroke. However, this information was collected by chart abstraction and should be interpreted with some caution.
References
1. Phillips SJ, Cameron K, Chung C. Stroke surveillance revisited. Can J Cardiol. 1993;9(suppl D):124D–125D.
2. Mayo N, Danys I Carlton J, et al. Accuracy of hospital discharge coding for stroke. Can J Cardiol. 1993;9(suppl D):121D–124D.
3. Jaigobin C, Silver FL. Stroke and pregnancy. Stroke. 2000;31:2948–2951.
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