How different were the populations compared (LD vs general population vs congestive heart failure) and how could this have impacted your conclusions?
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In addition to the limitation described above, I feel that another should also be incorporated.

In order to compare quality of life and healthcare utilization across various disease states and the general population, the authors extracted data from prior published literature. It is not clear how similar or different these populations were and there was not an effort to quantify these differences. A more appropriate means of comparison would have been to send the same survey as given to the Lyme Disease group to patients with CHF, asthma, diabetes, etc and make these comparisons within the same sample. Because the estimates provided likely come from such a different frame, these comparisons as presented are highly suspect and a description of this limitation would be useful in this section.

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We appreciate Dr. Donnelly's interest in our study of patients with chronic Lyme disease (CLD). His question suggests a basic misunderstanding of the Centers for Disease Control and Prevention (CDC) HRQoL metric. One of the values of using the CDC HRQoL is that, like other quality of life instruments (e.g. the SF-36), it permits the burdens of different diseases to be compared through the use of a standardized set of questions across different populations.1 The CDC HRQoL has been validated across different demographics and sample populations nationally and internationally. Thus, the physical and psychological impairment of patients with congestive heart failure, asthma, diabetes etc. and patients with CLD can be directly compared because all patients are responding to the exact same questions in the HRQoL. There is no frame shift here, and the comparisons of quality of life and healthcare utilization presented in our study are valid and reproducible across all these diseases because of the standardization of the HRQoL.


  1. Moriarty DG, Zack MM, Kobau R. The Centers for Disease Control and Prevention's Healthy Days Measures - population tracking of perceived physical and mental health over time. Health Qual Life Outcomes. 2003. Available from: http://www.ncbi.nlm.nih.gov/pubmed/14498988.
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