Reproducibility of human papillomavirus (HPV) typing on archived ThinPrep (Cytyc, Boxborough, MA) specimens was evaluated repeating Hybrid Capture II (HCII) (Digene, Gaithersburg, MD) testing after 25 to 40 months (mean, 31.3 months; group 1), 6 to 11 months (mean, 8.4 months; group 2), and 0 to 5 months (mean, 3.5 months; group 3). Another ThinPrep slide was prepared to evaluate cellularity and reproducibility of the cytologic diagnosis. The mean residual relative light units (RLU) calculated for each group showed a strong decrease of RLU values at the second typing (group 1, 21.69%; group 2, 26.47%; and group 3, 32.25% of original values). No residual HPV DNA was shown in group 1 in 8 (13%) of 60 cases or in groups 2 and 3 in 2 (3%) of 60 cases each. These cases were associated mostly with poor cellularity and reproducibility of the initial cytologic diagnosis in the final cytologic examination. Intergroup statistical analysis of mean relative percentages for cases with satisfactory residual cellularity revealed a significant difference only between groups 1 and 3 (P < .05).
Although mostly reproducible, HPV typing results by HCII on archived specimens are influenced by material consumption. In addition, results might be affected by some DNA degradation after long-term sample storage.