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Journal of Clinical Microbiology, September 2008, p. 2945-2949, Vol. 46, No. 9
0095-1137/08/$08.00+0     doi:10.1128/JCM.00359-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Diminished Human Immunodeficiency Virus Type 1 DNA Yield from Dried Blood Spots after Storage in a Humid Incubator at 37°C Compared to –20°C

University of Washington,¹ Seattle Children's Hospital Research Institute, Seattle, Washington,⁷ Virology Quality Assurance Laboratory, Rush University, Chicago, Illinois,² New England Research Institutes, Watertown,³ University of Massachusetts, Worcester, Massachusetts,¹⁰ University of Southern California,⁴ Childrens Hospital Los Angeles, Los Angeles, California,⁵ Louisiana State University, New Orleans, Louisiana,⁶ University of North Carolina, Chapel Hill, North Carolina,⁸ National Institute Allergy and Infectious Diseases,⁹ National Institute of Child Health and Human Development, Bethesda, Maryland,¹¹ University of Medicine and Dentistry of New Jersey, Newark, New Jersey,¹² University of the Witwatersrand, Johannesburg, South Africa,¹³

Received 22 February 2008/ Returned for modification 3 June 2008/ Accepted 29 June 2008

Collecting whole blood on filter paper simplifies the processing, transport, and storage of specimens used for the diagnosis of human immunodeficiency virus type 1 (HIV-1) and other tests. Specimens may be collected in tropical or rural areas with minimal facilities for handling specimens. To compare simulated tropical conditions with freezer storage, we examined the stability of HIV-1 DNA in dried blood spots (DBS) stored in humid heat and at –20°C. DBS were created by spotting 50-µl aliquots of whole blood on 903 filter paper. DNA was extracted from DBS at baseline and after 2, 6, or 12 months of storage at –20°C or at 37°C with 85% humidity. The DNA was tested undiluted or diluted using the Amplicor HIV-1 DNA PCR (Roche), version 1.5. Each reaction was scored positive, negative, or indeterminate based on optical density. Results were compared between storage conditions and over time. A total of 1,832 reactions from 916 DBS were analyzed, including 100 DBS at baseline, 418 stored at –20°C, and 398 stored at 37°C. A chi-square test showed fewer positive reactions for DBS stored at 37°C (55%) than for those stored at –20°C (78%) (P < 0.0001). Samples stored at –20°C showed little change in the probability of detection of HIV-1 DNA over time; the odds ratio (OR) was 0.93 after storage for 1 year. Samples stored at 37°C demonstrated a significant change in detection at 1 year (OR, 0.29). We conclude that exposure of DBS to 37°C and high humidity impaired the recovery of HIV-1 DNA from DBS, whereas DNA recovery was preserved when DBS were stored frozen.

Published ahead of print on 9 July 2008.