An apparent inconsistency exists in the data reported by Shadick and colleagues [1] in their retrospective cohort study of Lyme disease. The abstract notes neurocognitive impairment in four patients with a history of Lyme borreliosis. In the text, the authors report that 12 cases and only 5 controls scored more than 2 standard deviations from the mean on two or more memory tests. Finally, in Table 5, these figures are reversed, suggesting more abnormal results among controls. Perhaps these data are consistent and I have misinterpreted them, but, if so, others may also have done so. I ask that the authors clarify this issue.

Perhaps more importantly, the authors do not discuss recall bias, the most likely source of positive confounding of their data. The strongest statistical relations that the authors report pertain to subjective symptoms, specifically arthralgias and paresthesias. The emphasis placed on such symptoms is probably biased by a patient's knowledge of his or her Lyme disease history. In particular, patients in this study, informed that they received treatment for Lyme disease before optimal treatment protocols were established, might recall aches and pains that others might dismiss. Although the authors do discuss selection bias, another possible positive confounder, they conclude that the similarity of cases and controls mitigates this effect. However, of 18 contacts who declined participation, 14 were controls and only 4 were cases. Patients with a history of Lyme disease, particularly those with sequelae, may have been eager to participate. Misclassification is generally a negative confounder and is only of concern when statistical associations fail to reach significance. The authors seem justified in asserting that its effect was probably minimal.

In primary care, one encounters far more fear of Lyme disease than one sees actual infection. Although the findings reported here may ultimately prove to be valid, in the present form they are perhaps more likely to exacerbate that fear than they are to advance our understanding of the disease and its clinical manifestations. I would be disheartened to see these results reported in the lay press, where so much preliminary science appears.