COMPARATIVE EVALUATION OF THE DIAGNOSTIC EFFICACY OF MICROSCOPIC ANALYSIS AND PCR METHODS IN THE DIAGNOSIS OF HELMINTHIASIS
Boymurodova Feruza Jumanazar qizi
3rd-year student, Faculty of Medicine, Karshi State University
ABSTRACT
This article provides a comparative analysis of the diagnostic efficacy of traditional microscopic analysis methods and the modern molecular-genetic method — polymerase chain reaction (PCR) — used in diagnosing helminth infections. Studies show that while the sensitivity of microscopy is 45–65% in low-intensity invasions and latent helminthiasis, this indicator reaches 92–98% with the PCR method. The article thoroughly covers the analytical sensitivity, specificity, execution time, and cost-effectiveness of both methods.
Keywords: Helminthiasis, microscopy, Kato-Katz technique, polymerase chain reaction (PCR), analytical sensitivity, diagnostic specificity, DNA diagnostics.
INTRODUCTION
Helminthiases are among the most widespread parasitic diseases worldwide, particularly in developing countries and regions with tropical and subtropical climates. According to World Health Organization (WHO) data, more than 1.5 billion people are infected with soil-transmitted helminths (Ascaris lumbricoides, Trichuris trichiura, Ancylostoma duodenale).
Helminthiases constitute an important group of parasitic diseases affecting human health. Soil-transmitted helminthiases — specifically Ascaris lumbricoides, Trichuris trichiura, and hookworms — hold significant epidemiological importance in areas with inadequate sanitation. According to WHO data, these infections negatively impact nutrition and physical development in children.
In laboratory diagnostics, microscopic examination of stool has long served as a primary method. Identifying eggs, larvae, or other parasite stages based on morphological features is the main advantage of this technique. However, due to the intermittent shedding of parasites, low invasion intensity, and morphological similarities among certain species, a single negative microscopic examination cannot completely rule out infection. Consequently, molecular diagnostics — particularly PCR methods that allow direct detection of parasite DNA — have been widely applied in recent years. Nevertheless, implementing PCR uniformly across all laboratories requires specialized equipment, consumables, quality control, and qualified personnel.
MATERIALS AND METHODS
To evaluate the efficacy of diagnostic methods used in detecting helminthiases, parameters within the following two groups of methods were analyzed:
Microscopic methods:
Kato-Katz technique: Counting the number of eggs per gram of stool using the thick smear technique.
Ether-formalin sedimentation method: Concentrating parasite eggs and cysts.
Molecular-genetic method:
Real-Time PCR: Amplifying and identifying specific parasite DNA sequences (e.g., 18S rRNA or ITS2 gene regions).
Diagnostic efficacy was evaluated based on sensitivity, specificity, positive predictive value, and negative predictive value criteria.
RESULTS AND DISCUSSION
The turnaround time for results is 30–60 minutes per sample and 2–4 hours for large batches.
Microscopic examination of stool remains one of the most widely used laboratory methods for detecting helminthiases. Helminth eggs or larvae can be detected using simple smears, concentration techniques, and methods like Kato–Katz. The most significant advantage of microscopy is its low cost and technical simplicity under laboratory conditions. Furthermore, direct morphological examination allows for the visual identification of parasite eggs or larvae. The Kato–Katz technique, in addition to detecting eggs in certain soil-transmitted helminthiases, serves to assess the intensity of infection.
PCR is a molecular method based on amplifying a target-specific DNA fragment. The primary advantage of PCR in helminth diagnostics is the ability to detect parasite DNA in biological samples without waiting for a stage visible under a microscope.
This feature is particularly crucial in low-intensity infections and in the differential diagnosis of morphologically similar species.
Modern molecular diagnostic reviews describe PCR-based approaches for helminths such as Ascaris lumbricoides, Trichuris trichiura, hookworms, and Strongyloides stercoralis. Factors such as sample collection, DNA extraction, PCR inhibitors in stool, risk of contamination, primer specificity to the target, and standardization of laboratory protocols directly influence the final result. Additionally, since molecular methods detect parasite DNA, the clinical interpretation of results must be evaluated alongside patient symptoms and epidemiological data.
CONCLUSION
In the diagnosis of helminthiases, microscopic examination and PCR are not mutually exclusive but rather complementary methods. Microscopic analysis retains its importance as a primary method for mass screening and routine checkups due to its cost-effectiveness, lack of requirement for complex reagents, and simplicity.
Polymerase chain reaction (PCR) possesses high sensitivity and specificity, making it the method of choice in acute stages, latent infections, low invasion levels, and cases where differential diagnosis is challenging. However, its high cost, specialized laboratory infrastructure requirements, and high standards for quality control limit its widespread implementation. Combining microscopic and PCR methods in a phased approach improves diagnostic accuracy while ensuring optimal utilization of laboratory resources.
