RLU/CO Value Are Dependent on Age

The effect of age on Hybrid Capture 2 (HC2) tests initially falling within the equivocal range has not been determined. We identified 359 cervicovaginal liquid cytology specimens with initial equivocal values. First and second retest relative light units/ cutoff (RLU/CO) values were compared for women of 3 different age groups (15-29, 30-49, and ≥50 years). The proportion of first retests with an RLU/CO of less than 1 increased with age (P < .001). Of the 56 second retests performed, only 4 had an RLU/CO of 1 or more. The proportion of “positive” HC2 results following the current HC2 algorithm decreased with increasing age (P < .001), showing that HC2 test results after an initial equivocal value are dependent on age. Follow-up demonstrated cervical intraepithelial neoplasia grade 2 or worse (CIN2+) in 6 (5.9%) women 15 to 29 years old and in 5 (6.3%) women 30 to 49 years old. No CIN2+ was found on follow-up of 34 of 57 women 50 years and older. These results likely reflect human papillomavirus infection prevalence and question the use of identical cutoff values regardless of age for detection of CIN2+. Persistent cervical infection with high-risk human papillomavirus (HPV) types causes cervical cancer and its precursor lesions.1 HPV DNA testing, which has greater sensitivity but lower specificity for cervical intraepithelial neoplasia grade 2 or worse (CIN2+) compared with cytology, was first incorporated in the American Cancer Society (ACS) cervical cancer screening guidelines in 2002.2 According to the most recent guidelines by the ACS, the American Society for Colposcopy and Cervical Pathology, and the American Society for Clinical Pathology, HPV DNA cotesting is recommended in women 30 to 65 years old, allowing for an increased screening interval of 5 years.3 However, the performance characteristics vary among different commercially available HPV DNA tests, and excessive analytic sensitivity is currently deemed a significant concern due to poorer specificity.4 The Hybrid Capture 2 (HC2) system (Qiagen, Valencia, CA) is a widely used Food and Drug Administration–approved test for detection of HPV DNA by probe hybridization and chemiluminescence. A liquid cervicovaginal specimen’s signal is measured in relative light units (RLU) and compared with the average signal of positive controls provided by the manufacturer. According to manufacturer recommendations, the RLU/cutoff (RLU/CO) ratio value is considered positive when greater than or equal to 1, corresponding to a concentration of 1 pg/mL.5 However, an initial RLU/CO value between 1 and less than 2.5 is considered equivocal and prompts a confirmatory retest. If a first retest is negative, then the result of a second retest is considered the final result.5 HC2 performance at different cutoff values has been addressed by several studies. Some point out that higher HC2 cutoff values (up to RLU/ CO ≥10) would result in beneficial reductions in positive HC2 Upon completion of this activity you will be able to: • describe the relationship between age and human papillomavirus (HPV) infection prevalence in different populations. • describe the Hybrid Capture 2 (HC2) test interpretative algorithm. • effectively correlate HPV infection prevalence, HC2 relative light units/ cutoff values, and age as they relate to detection of CIN2+. The ASCP is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The ASCP designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 Credit TM per article. Physicians should claim only the credit commensurate with the extent of their participation in the activity. This activity qualifies as an American Board of Pathology Maintenance of Certification Part II Self-Assessment Module. The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose. Questions appear on p 691. Exam is located at www.ascp.org/ajcpcme.