A systematic review of high quality diagnostic tests for Chagas disease

Abstract

Background: There is significant heterogeneity in reported sensitivities and specificities of diagnostic serological assays for Chagas disease, as might be expected from studies that vary widely according to setting, research design, antigens employed, and reference standard. The purpose of this study is to summarize the reported accuracy of serological assays and to identify sources of heterogeneity including quality of research design. To avoid associated spectrum bias, our analysis was limited to cohort studies.

Methods: We completed a search of PubMed, a bibliographic review of potentially relevant articles, and a review of articles identified by a study author involved in this area of research. Studies were limited to prospective cohort studies of adults published since 1985. Measures of diagnostic accuracy were pooled using a Der Simonian Laird Random Effects Model. A subgroup analysis and meta regression were employed to identify sources of heterogeneity. The QUADAS tool was used to assess quality of included studies and Begg's funnel plot was used to assess publication bias.

Results: Eighteen studies and 61 assays were included in the final analysis. Significant heterogeneity was found in all pre-determined subgroups. Overall sensitivity was 90% (95% CI: 89%-91%) and overall specificity was 98% (95% CI: 98%-98%).

Conclusion: Sensitivity and specificity of serological assays for the diagnosis of Chagas disease appear less accurate than previously thought. Suggestions to improve the accuracy of reporting include the enrollment of patients in a prospective manner, double blinding, and providing an explicit method of addressing subjects that have an indeterminate diagnosis by either the reference standard or index test.

Figure 1. Overall percentage of studies that met QUADAS guidelines.

* RS =  Reference standard.

Figure 2. Quality assessment of individual studies using QUADAS tool.

* RS =  Reference standard.

Figure 3. Summary receiver operating characteristic curve with 95% CI for all tests.

Each circle represents the sensitivity and specificity of an individual assay. The size of the circles reflects the number of patients in a study. Area under the curve = 0.99.

Figure 4. Forest plot of sensitivity and specificity for all studies.

Figure 5. Assessment of publication bias with Begg's funnel plot.

The measure of effect is ln(DOR) and the standard error of the ln(DOR) is the measure of variance. Note relative deficit of smaller studies showing lower accuracy in the lower right quadrant of the figure.