ENHANCEMENT OF VARICELLA-ZOSTER VIRUS DETECTION IN A-549 SHELL VIALS BY USE OF FREEZE-THAWED SPECIMENS, EXTENDED INCUBATION, AND A CENTRIFUGED, NOT INCUBATED DIRECT-DETECTION METHOD

A total of 95 clinical samples were cultured for periods of 2 and 7 da ys in centrifuged A-549 shell vials before and after freezing and thaw ing of specimens. In addition, centrifuged A-549 shell vials were test ed directly for varicella-zoster virus without incubation using a dire ct fluorescent antibody (DFAI technique. Twenty-seven specimens were p ositive by at least one method. The sensitivity for DFA on unincubated A-549 shell vials was 85.2%; for unfrozen 2-day cultures, 88.9%; for unfrozen 7-day cultures, 92.6%; for freeze-thaw 2-day cultures, es, 92 .6%; and for freeze-thaw 7-day cultures, 96.3%. Freeze-thawed specimen s cultured for 7 days yielded the high est number of positive results with conspicuous cell-to-cell spread as a sign of viral replication. ( C) 1998 Elsevier Science Inc.