Tuberculosis (TB) is an unignorable global health issue that claims about 1.4 million lives per annum. The contribution of smear-negative but culture-positive pulmonary TB diagnosis to global TB transmission is around 12.6%. Traditional TB diagnosis via smear microscopy, recognizes cases by detecting a minimum of 5,000 to 10,000 bacilli per milliliter (CFU/ml) of sputum, which leads to missed and false positive cases. By contrast, GeneXpert technology with a limit of detection (LOD) of 131–250 CFU/ml in sputum samples offers a more advanced alternative for early TB and drug-resistant TB detection.
Since 2013, Ghana Health Service has integrated GeneXpert MTB/RIF diagnostics into all regional hospitals in the country. However, no comprehensive analysis comparing performance between microscopy and GeneXpert TB diagnosis across Ghana’s healthcare facilities has been hitherto reported. A recent study undertook this task by comparing routine TB diagnoses conducted through microscopy and Xpert MTB from 2016 to 2020 at the Cape Coast Teaching Hospital (CCTH).
Sputum specimens from suspected TB cases were collected and processed within 24 hours. The samples, post decontamination, were used for creating fixed smears for microscopy and GeneXpert MTB/RIF analysis. The data were analyzed using GraphPad Prism.
The study found that 50.11% of those reporting to the TB clinic for suspected TB diagnosis were females. The smear-positive cases for first and second sputum were 6.6% and 6.07% respectively. The Xpert MTB-RIF diagnosis detected TB in 2.93% of the first and 5.44% of the second smear-negative samples. It was also noted that a small proportion of smears that tested negative were false negatives. The study concluded that the GeneXpert assay demonstrated higher sensitivity compared to traditional smear microscopy for detecting TB.
Given the alarming rate of TB infections and the growing issue of drug-resistance, rapid TB diagnosis remains a daunting challenge, especially in low and middle-income countries where over 90% of TB cases are reported. Even though culture method is often considered the gold standard for TB diagnosis, it demands complex lab procedures and expensive safety equipment, proving difficult to operate in resource-limited nations.
In light of these, more sensitive diagnostic tools with faster turnaround times are a pressing requirement. GeneXpert MTB/RIF assay, a molecular-based diagnostic tool, recommended widely due to its high sensitivity and much shorter turnaround time, may provide the solution for this predicament. It also offers minimal safety concerns and proves useful in TB diagnosis, indicating a bright future for it in the global fight against TB.
Source: https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-024-09566-9