PCRteszt

PCRteszt, short for polymerase chain reaction test, is a molecular diagnostic method used to detect the genetic material of a pathogen in a clinical sample. The technique amplifies targeted DNA sequences so that even very small amounts of material become detectable. For RNA viruses such as SARS-CoV-2, the test is typically performed as real-time reverse transcription PCR (RT-PCR), which converts RNA into cDNA and then amplifies selected regions.

Procedure: a specimen is collected (commonly a nasopharyngeal or oropharyngeal swab, or saliva). RNA is extracted and reverse-transcribed to cDNA. The DNA is amplified through cycles of heating and cooling, with fluorescent signals indicating amplification in real time. A positive result reveals the presence of the target sequence; a negative result indicates no detectable target within the defined cycling threshold. Ct values can estimate viral load in some assays.

Interpretation and limitations: RT-PCR is highly specific and sensitive when samples are collected properly and processed promptly. False negatives may occur due to timing, poor sampling, or technical issues. False positives are uncommon but can arise from contamination. Detecting RNA does not necessarily imply infectious virus, especially in later stages of infection.

Applications and quality: PCR tests are used for diagnosing active infections, guiding treatment, and screening programs. They require specialized laboratories and trained personnel, with strict quality control, controls, validation, and adherence to regulatory guidelines from health authorities.

History: The polymerase chain reaction was developed in the 1980s by Kary Mullis and has become a cornerstone of clinical diagnostics, with real-time RT-PCR becoming common in infectious disease testing during the 1990s and beyond.