Evaluating a clinical categorization schema for chronic Lyme disease

Background: Lyme disease is an emerging infectious disease. Outside the framework of CDC-defined early and late disease, chronic Lyme disease remains controversial and confusing. A recently proposed schema categorizes the spectrum of patients presenting for evaluation of this condition, including those with alternative diagnoses, medically unexplained symptoms, and illnesses possibly related to prior Lyme disease (Feder et al., NEJM, 2007). However, the utility of these categories for clinical or research purposes has not been examined.

Methods: A consecutive case series of patients presenting to a community-based Lyme referral practice in Maryland revealed 216 patients with chronic symptoms not meeting CDC criteria for late Lyme disease. Patient histories were gathered through retrospective chart review and self-report. Category assignment was based on inclusion/exclusion criteria in the aforementioned article.

Results: 50% could not be assigned a category due to incomplete clinical evaluation at disease onset. An additional 18% had been appropriately evaluated but specific inclusion/exclusion criteria left them unassigned. This latter subset was compared to those assigned a category; they were significantly more likely to have had prior CDC-defined early Lyme (OR = 8.28 [3.38-20.29]), initial objective clinical findings (OR=16.40 [6.14-44.05]), and prior antibiotic exposure (OR=4.18 [1.63-10.76]).

Conclusion: The proposed categories for chronic Lyme disease were inadequate in classifying the majority of our patients. Incomplete initial evaluations, as well as the identification of an additional unclassifiable subset, render this schema problematic. Of most concern for clinical and research applications, these categories may exclude those with more compelling evidence for prior Lyme exposure.