Dried blood spot specimen quality and validation of a new pre-analytical processing method for qualitative HIV-1 PCR, KwaZulu-Natal, South Africa

ABSTRACT

Background: Poor quality dried blood spot (DBS) specimens are usually rejected by virology laboratories; affecting early infant diagnosis of HIV. The practice of combining two incompletely-filled DBS in one specimen preparation tube during pre-analytical specimen processing (i.e.; the two-spot method) has been implemented to reduce the number of specimens being rejected for insufficient volume.Objectives: This study analysed laboratory data to describe the quality of DBS specimens and the use of the two-spot method over a one-year period; then validated the two-spot method against the standard (one-spot) method.Methods: Data on HIV-1 PCR test requests submitted in 2014 to the Department of Virology at Inkosi Albert Luthuli Central Hospital in KwaZulu-Natal province; South Africa were analysed to describe reasons for specimen rejection; as well as results of the two-spot method. The accuracy; lower limit of detection and precision of the two-spot method were assessed.Results: Of the 88 481 specimens received; 3.7% were rejected for pre-analytical problems. Of those; 48.9% were rejected as a result of insufficient specimen volume. Two health facilities had significantly more specimen rejections than other facilities. The two-spot method prevented 10 504 specimen rejections. The Pearson correlation coefficient comparing the standard to the two-spot method was 0.997.Conclusions: The two-spot method was comparable with the standard method of pre-analytical specimen processing. Two health facilities were identified for targeted retraining on specimen quality. The two-spot method of DBS specimen processing can be used as an adjunct to retraining; to reduce the number of specimens rejected and improve linkage to care