Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1386 page)

   Methods

   Branched DNA assay (bDNA; Siemens): A signal amplification technology that detects the presence of specific nucleic acids by measuring the signal generated by branched, labeled DNA probes; a reliable method that provides consistent results in the higher range of the assay.

   Real-time PCR (Cobas AmpliPrep/Cobas TaqMan, Roche): Reverse transcription is followed by PCR amplification and quantification of the targeted DNA molecule; generally offers both a wider range of quantification and a lower limit of detection than the bDNA method.

   Used in the management of HIV-1–infected individuals undergoing antiviral therapy.

   Limitations

   PCR inhibitors in the specimen may lead to underestimation of viral quantitation or false-negative results in rare cases.

   For consistency in interpretation of patient results, the same methodology should be used in patient management.

HUMAN PAPILLOMAVIRUS (HPV) MOLECULAR TESTING
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   Definition

   HPV test provides information to clinicians on a patient’s risk for developing cervical cancer. There are currently five FDA-approved HPV assays that are detecting high-risk (HR) genital HPV types that are commonly associated with cervical cancer. Hybrid Capture 2 High Risk HPV DNA Test (Digene, Qiagen) detects 13 HR-HPV types; Cervista
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HPV HR (Third Wave Technologies, Hologic) detects 14 HR genital HPV types; Cervista HPV 16/18 identifies DNA types 16 and 18; Cobas HPV Test (Roche) specifically identifies types HPV 16 and HPV 18 while concurrently detecting the rest of the high risk types. These four tests detect HPV viral DNA in cervical cells collected during the liquid-based Pap test (“pap smear”). APTIMA HPV assay with the TIGRIS DTS System (Gen-Probe) is the first FDA-approved assay that detects the messenger RNA of two HPV viral oncogenes, E6 and E7. Although HPV infection is very common, and usually self-resolving, if HPV RNA is present, the patient is in a higher risk category for developing cervical cancer than if HPV is not detected.

   Use

   Guidelines for cervical cancer screening that include HPV DNA testing issued by the American Society for Colposcopy and Cervical Pathology (ASCCP), the Centers for Disease Control and Prevention, and the American College of Obstetricians and Gynecologists recommend that

   HPV molecular testing is not used for evaluation of women younger than 21 years—most HPV infections in this age group are transient and will be cleared by the immune system.