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November 1989

Ischemic Injury and Necrotizing Tracheobronchitis

Author Affiliations

9016 First Ave Silver Spring, MD 20910

Am J Dis Child. 1989;143(11):1259-1260. doi:10.1001/archpedi.1989.02150230017005

Sir.—The article by Hanson et all in the October 1988 issue of AJDC somewhat supported a personal belief that ischemic injury is involved in the propagation of necrotizing tracheobronchitis (NTB). However, I do not believe that their data justify a causal relationship, as the title of the article would imply. Although 58 infants with NTB had either profound hypotension or low 5-minute Apgar scores (the "ischemia" factors that differentiated them from the controls), the remaining 64 affected infants (54%) had neither of these factors. Furthermore, the authors state that their data were analyzed with "a two-tailed t test."1 I suspect that they actually meant that X2 analysis was used. Simplistically, the t distribution is a method of com= paring two group means, while the X2 statistic compares rates or frequencies of discrete findings. The P values presented in the tables are actually those that one would

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