Successful HCV genotyping of previously failed and low viral load specimens using an HCV RNA qualitative assay based on transcription-mediated amplification in conjunction with the line probe assay.
BACKGROUND
Hepatitis C virus (HCV) genotyping is a critical part of the diagnostic work-up for chronic hepatitis C. The VERSANT HCV line probe assay (LiPA) marketed by Bayer Corporation requires PCR-derived amplicons for genotyping usually obtained from commercial assays, including Amplicor HCV 2.0 (Amplicor 2.0), Amplicor HCV Monitor 2.0, or SuperQuant. Occasionally, PCR-based methods in conjunction with LiPA fail to give a genotyping result. Although most genotyping failures occur among low viral load specimens, some occur in specimens with relatively high viral loads. The Bayer HCV RNA Qualitative assay (HCV TMA), with a limit of detection of approximately 5-10 IU/ml, is more sensitive than other commercial assays.


OBJECTIVE
An HCV genotyping protocol using HCV TMA linked with LiPA (TMA-LiPA) was developed and tested for ability to genotype samples that had previously failed genotyping by PCR-based methods in conjunction with LiPA.


METHODS
Clinical specimens were obtained from eight independent laboratories in Canada and the US and tested with TMA-LiPA at the Bayer Reference Testing Laboratory. Specimens included those that failed to produce a genotype result when a PCR-based assay was used in conjunction with LiPA and specimens for which genotyping was not attempted because the viral load was below the validated cut-off determined in the laboratory of origin.


CONCLUSIONS
TMA-LiPA successfully genotyped 68 of 75 (90.7%) specimens that had failed genotyping by PCR-based methods used in conjunction with LiPA and 36 of 40 (90.0%) specimens that were rejected for genotyping due to low viral load. Moreover, TMA-LiPA assigned subtype for 79 of 107 (73.8%) specimens. Our TMA-LiPA results reflected the distribution of HCV genotypes found in North America, and were 100% concordant with those of Amplicor 2.0 in conjunction with LiPA for control specimens genotyped by both assays. TMA-LiPA may prove useful both in optimizing LiPA performance and genotyping patient specimens.
Comanor
Lorraine
L
1801 Waverley Street, Palo Alto, CA 94301, USA. lorraine.comanor.b@bayer.com
Elkin
Claudia
C
Leung
Kimmy
K
Krajden
Mel
M
Kronquist
Kathryn
K
Nicolas
Keith
K
Horansky
Evelyn
E
deMedina
Maria
M
Kittichai
Promrat
P
Sablon
Erwin
E
Ziermann
Rainer
R
Sherlock
Chris
C
D005838:Genotype; D016174:Hepacivirus / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D006526:Hepatitis C / Q000175:diagnosis* / Q000821:virology; D006801:Humans; D015336:Molecular Probe Techniques; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D012367:RNA, Viral / Q000032:analysis* / Q000235:genetics; D012680:Sensitivity and Specificity; D019562:Viral Load
D012367:RNA, Viral