Utilization of polymerase chain reaction on archival cytologic material: a comparison with fresh material with...

Use of the polymerase chain reaction (PCR) for the detection of B- and T-cell clonality, Epstein-Barr virus (EBV) and Human Herpes Virus 8 (HHV 8) infection is gaining increasing importance as a diagnostic modality. These tests are usually performed on fresh specimens. There are instances when fresh material is not available and there is a clinical utility for the performance of PCR on archival material via slide scrape lysates (SSL). However, the suitability of archival material may be questioned. Records were searched for all archival cytology cases submitted for SSL molecular diagnostics tests since 1998. Results for each case were analyzed for PCR amplification status and individual test results. A randomly chosen control group of equivalent cytologic samples submitted fresh was evaluated for comparison of amplification status. In all, 241 PCR runs were performed on SSL of archival material from 112 cytologic samples (89 cerebrospinal fluids (CSFs), 13 fine-needle aspirates (FNAs), 10 effusions). Out of these samples, 95 (85%) had amplifiable DNA, as assessed by a positive reaction for glyceraldehyde phosphate dehydrogenase (GAPDH). For the control group, 320 PCR runs were performed on 112 fresh cytologic samples (89 CSFs, 13 FNAs, 10 effusions). In total, 102 samples (91%) had amplifiable DNA. There was no statistical difference in the amplification yield between the two groups (P = 0.2177). A morphologic review of 16 of the 17 SSL archival cytologic cases that did not show amplification revealed 11/16 to be of sparse cellularity. Molecular diagnostic tests are performed routinely on fresh cytologic samples with excellent results. At times critical decisions on patient care may need to be made when fresh tissue is not available for molecular diagnostic tests. SSL of archival cytologic material can be used with excellent results for molecular diagnostic tests when fresh material is not available or when the cytologic diagnosis needs further clarification.