Influenza virus detection in clinical specimens

Area of Science:

• Virology
• Clinical Diagnostics
• Molecular Biology

Background:

• Accurate influenza virus detection is vital for patient management and public health.
• Various diagnostic methods exist, each with potential limitations in sensitivity and specificity.
• Specimen handling and storage conditions can significantly impact the reliability of diagnostic tests.

Purpose of the Study:

• To compare the effectiveness of molecular hybridization (MH), ELISA, virus isolation, and immunofluorescence (IF) for detecting influenza A (H1N1) and influenza A (H3N2) viruses.
• To evaluate the influence of specimen sampling and storage conditions on diagnostic test performance.
• To determine the most reliable method for influenza virus detection in nasopharyngeal swabs.

Main Methods:

• Nasopharyngeal swabs from 63 patients were tested using MH, ELISA, virus isolation, and IF.
• Specimens were grouped based on storage conditions: -70°C without thawing, -20°C with repeated thawing, and prolonged storage after repeated thawing.
• Specificity was assessed using samples from patients with influenza B and other respiratory viruses.

Main Results:

• At -70°C without thawing, MH detected RNA in 72% and ELISA detected antigen in 86% of specimens.
• IF and virus isolation showed lower detection rates (27% and 22%, respectively).
• Under suboptimal storage conditions (-20°C with thawing), MH sensitivity decreased significantly (9% to 0%), while ELISA remained effective (71-80%).

Conclusions:

• ELISA demonstrates superior performance and robustness for influenza A virus detection in nasopharyngeal swabs, even under challenging storage conditions.
• Molecular hybridization and immunofluorescence are highly sensitive to specimen handling and storage, limiting their utility in resource-limited or field settings.
• Optimal specimen storage at -70°C is recommended for methods like MH, but ELISA offers a more practical alternative for routine diagnostics.