# Combination of Individual Tests to Improve Diagnostic Accuracy in Chlamydia trachomatis Detection

## TL;DR

This study evaluates combinations of diagnostic tests for Chlamydia trachomatis to improve detection accuracy, finding that some combinations do not outperform a single rapid test.

## Contribution

The study provides insights into optimal test combinations for diagnosing Chlamydia trachomatis, emphasizing the limitations of multi-test approaches.

## Key findings

- Combinations of DIF + RT and RT + IgG do not improve diagnostic efficiency over a single rapid test.
- RT/IgA combination shows high specificity and total diagnostic accuracy of 93.00%.
- The extended Youden index highlights RT/IgA as the best combination with a value of 94.60%.

## Abstract

Background and Objectives: Chlamydial infection is the most common asymptomatic infection worldwide. Despite all national programs, strategies and guidelines, chlamydial infection is still the leading infection worldwide, especially in young populations. We have tried to summarize the best diagnostic tools for its detection. Materials and Methods: In the study, 225 sexually active patients who were tested for chlamydial infection at the Institute of Public Health Kragujevac participated. Results: Combinations of direct immunofluorescence (DIF) and a rapid lateral immunochromatographic test (RT) and combinations of an RT and immunoglobulin G (IgG) do not improve diagnostic efficiency when compared to a rapid test that individually had the best parameters. In situations that require high specificity, the recommended combination is RT/IgA, which as a highly specific test has few false positive results, while the combinations of DIF + RT and RT + IgG, although showing a specificity of 100%, have low sensitivity (33.30%), due to which we prefer the RT/IgA combination. The combinations DIF + RT, DIF + RT + IgG and RT + IgG, although with low sensitivity, have the highest values of specificity, and the positive predictive value (PPV) and negative predictive value (NPV) show the highest values of the extended Youden index of 130.30% and the highest values of total diagnostic accuracy of 97.00%. Based on the results of the extended Youden index, taking into account PPV and NPV, the RT/IgA combination shows the highest value of 94.60%, as well as the highest value of total diagnostic accuracy of 93.00%. Conclusions: “Two or more positive tests” or “any test positive” did not improve the diagnostic efficiency compared to a single “rapid test”.