The diagnostic accuracy of point-of-care nucleic acid-based isothermal amplification assays for scrub typhus: a systematic review and meta-analysis

Introduction: The diagnosis and detection of pathogens such as Rickettsia and Orientia is a cause of major concern among the public health community. Unavailability of rapid, cost-effective diagnostic assays contributes to delayed diagnosis and timely treatment. Using the methodology of systematic reviewing and meta-analysis, the study aimed to synthesize and compare the diagnostic performances of all the available isothermal assays for the detection of classical rickettsial diseases.

Methods: Studies were retrieved from PubMed and Scopus, and selection and screening were conducted using pre-determined inclusion and exclusion criteria. Analysis was performed using Meta-DiSc 2.0 for the assessment and comparison of diagnostic performance of the isothermal assays.

Results: Overall, six studies were selected as a part of this systematic review. All the selected studies (n = 6) optimized LAMP as their index test to detect scrub typhus. The quality assessment of the selected studies revealed only (n = 1) study to be of poor quality with a QUADAS-2 score of (<2). Meta-analysis revealed the pooled sensitivity of LAMP to be 66% [95% CI (0.40-0.85)] with a pooled specificity of 94% [95% CI (0.81-0.98)]. LAMP was estimated with a positive likelihood ratio of 8.3 [95% CI (3.8-18.1)] and a negative likelihood ratio of 0.3 [95% CI (0.2-0.7)] with a false positivity rate of 0.07 [95% CI (0.02-0.2)]. The diagnostic odds ratio was reported to be 21.96 [95% CI (10.2-47.3)]. Due to severe heterogeneity in the body of evidence (I ² = 0.77), a meta-regression was performed with certain covariates to explore the potential causes. A case-control design was found to exaggerate the sensitivity {0.84 [95% CI (0.5-0.9)]} and specificity {0.73 [95% CI (0.6-0.8)]}.

Conclusion: The findings reveal subpar performance of LAMP for the detection of scrub typhus. Active research and development focused on optimization of novel molecular diagnosis that are efficient, rapid, and cost-effective shall foster timely diagnosis and aid in reduction of the overall burden of scrub typhus.

Protocol and registration: A detailed protocol of this review is registered and available in Prospero at: https://www.crd.york.ac.uk/prospero/. (registration number CRD42024511706).