A systematic review 1 including 6 studies was abstracted in DARE.
Two studies were included in the assessment of the sensitivity, specificity and likelihood ratios of enzyme-linked immunoassay. In early Lyme disease the random effects combined estimates were 95% for sensitivity and 81% for specificity, with a positive likelihood ratio of 8.42 and negative likelihood ratio of 0.44. For late Lyme disease the random effects combined estimates were 95% for sensitivity and 81% for specificity, with a positive likelihood ratio of 5.01 and negative likelihood ratio of 0.06. These indicate that if the patient has clinical symptoms and signs that are consistent wity Lyme disease (a pre-test probability that exceeds 0.20) the information provided by ELISA is clinically useful. If the result is positive the disease is ruled in and if the result is negative the disease is ruled out. In non-specific clinical presentations testing is more likely to mislead than to help establish the correct diagnosis.
Four studies were included in the assessment of Western blotting. Two of these studies showed that Western blotting was useful in adding information to positive or indeterminate ELISA tests. The combined likelihood ratio for indeterminate results from ELISA alone was 1.05. The addition of positive Western blot increased the combined likelihood ratio to 11.7, while the addition of negative Western blots to netative or indeterminate ELISA resulted in a combined likelihood ratio of 0.08. In effect in indeterminate result using ELISA, where the probability of disease has increased from 0.50 pre-test to 0.51 post-test, the addition of a positive Western blot increases to probability to 0.92.
Comment: The quality of evidence is upgraded by large magnitude of effect. As studies were limited to North America, due to the differences in the nature of the disease in other areas, the results will have limited generalisability.
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