Hybridization Protection Assay (HPA) uses a specific oligonucleotide probe labeled with an acridinium ester detector molecule that emits a chemiluminescent signal. The probe hybridizes with either target rRNA in non-simplified tests, or amplicons produced in TMA reactions. Detection does not require washing steps, making the HPA format as easy to perform as the simplest immunoassay, with the superior specificity of DNA probes.