Line Probe Assay for Detecting Drug Resistance

Technical Methodology

• The line probe assay operates through a hybridization-based detection system, using PCR amplification of target DNA sequences, followed by hybridization of the amplified products to specific oligonucleotide probes immobilized on membrane strips 2, 3
• The assay can detect single nucleotide mismatches and contains a series of short membrane-bound oligonucleotide probes that bind to specific mutation sites 2

Clinical Applications

• The American Gastroenterological Association recommends line probe assays for detecting mutations in the HBV polymerase gene that confer resistance to nucleoside/nucleotide analogs like lamivudine, adefovir, and entecavir 1, 4
• Line probe assays can detect viral mutants that constitute as little as 5% of the total viral population, making it more sensitive than direct PCR sequencing which requires approximately 20% 2, 3

Critical Limitations and Pitfalls

• The line probe assay cannot detect unknown or novel mutations - only identifies mutations for which specific probes have been designed 2, 3
• The American Association for the Study of Liver Diseases notes that molecular results from line probe assays must always be confirmed by phenotypic culture-based drug susceptibility testing 1, 4