Ciprofloxacin resistance does not affect duration of domestically acquired campylobacteriosis.

Correspondence Table 1. Mean duration versus resistance and foreign-travel status of cases. Foreign travel Resistance to ciprofloxacin Yes No Yes 8.1 days (n p 29) 7.6 days (n p 48) No 6.9 days (n p 41) 6.9 days (n p 529) NOTE. The data do not include patients not reporting diarrhea, those with continuing diarrhea, those unable to estimate duration of diarrhea, or those not responding to the foreign-travel question. To the Editor—In their article " Prolonged Diarrhea Due to Ciprofloxacin-Resistant Campylobacter Infection " [1], Nelson et al. comment, " Although human infections with ciprofloxacin-resistant Campylobac-ter have become increasingly common, the human health consequences of such infections are not well described " (p. 1150). They then present analyses indicating that " persons with ciprofloxacin-resistant infection had a longer mean duration of diarrhea than did the persons with ciprofloxacin-susceptible infection (P p .01); this effect was independent of foreign travel " (p. 1150). They conclude, " Persons with ciprofloxacin-resistant Campylo-bacter infection have a longer duration of diarrhea than do persons with ciprofloxa-cin-susceptible Campylobacter infection. Additional efforts are needed to preserve the efficacy of fluoroquinolones " (p. 1150). We have a number of concerns with these analyses. The following comments address some of them. Reexamining the raw data raises questions about the validity and general applicability of the stated conclusions and interpretations. Table 1 shows the mean number of illness-days (and no. of cases) of Campylobacter infection that (1) are acquired via foreign travel versus domestically and (2) are ciprofloxacin resistant versus ciprofloxacin susceptible. This table shows the unadjusted data, without adjustment for the additional subset-selection and statistical-modeling steps used by Nelson et al. Although foreign travel is strongly associated with resistance to ciprofloxacin, and also with longer mean duration of diarrhea, resistance to ciprofloxacin is clearly not associated with longer mean duration of diarrhea among cases of domestically acquired campylobacteriosis. Any analysis that begins with crude data showing no apparent effect but that ends by concluding that there is a significant effect for some subsets of subjects must be especially diligent in the reporting of model diagnostics, as well as in correcting for potential model-selection bias, variable-selection and-coding biases, data subset– selection bias, and multiple-testing biases , all of which can threaten study validity by producing an excessive number of false-positives [2, 3]. Nelson et al. do not report such recommended diag-nostics and corrections, which leaves open the possibility that the …