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

Abstract

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).

Keywords: Orientia; diagnostics; loop-mediated isothermal amplification; meta-analysis; scrub typhus.

Figure 1

PRISMA flowchart depicting screening and selection of studies for the systematic review and meta-analysis in accordance with PRISMA 2020 checklist. The PRISMA 2020 figure is a template provided at (https://www.prisma-statement.org/prisma-2020-flow-diagram) to be used by researchers conducting Systematic reviews. It is publicly available and is an essential part of reporting standards for systematic review and meta-analysis.

Figure 2

Assessment of the selected studies for quality and risk of bias using the quality assessment of diagnostic accuracy studies-2 (QUADAS-2) toolkit. Each study was assessed for (i) applicability and (ii) risk of bias and, allotted scores in every domain with a final score are depicted in (iii) overall QUADAS-2 score.

Figure 3

Forest plot depicting pooled effect estimates of (A) sensitivity and (B) specificity in the meta-analysis.

Figure 4

Graphical representation of the diagnostic performance of LAMP as an isothermal assay for the detection of scrub typhus using summary receiver operating curve (SROC).

Figure 5

Pictorial representation of diagnostic performance of LAMP for detecting scrub typhus using a hypothetical population model. [Note: proxy prevalence of scrub typhus is taken to be ~50%; n = 100].