Figure 1. Study design flow-chart.

Tumors from the total study population (n=209) were tested with HPV L1 Genotyping method. All samples with negative or invalid results were rerun (n=37). Samples with two-time negative or invalid results using the L1 based approach were analyzed with a HPV E6/E7 genotyping method (n=33). Patient samples with negative results after both genotyping methods and with available alternative tissue block were reanalyzed twice with method targeting L1 and once with methods targeting E6/E7 (n=12). HPV negative patient samples without alternative material available or with a consistent negative result after genotyping were evaluated by pathologist (n=20). After repeated testing, use of alternate genotyping approach and exclusion of reclassified cases or cases with insufficient tumor material, 93% (188/203) of the tumors were positive for HPV.