Dried tube specimens: A simple and cost-effective method for preparation of HIV proficiency testing panels and quality control materials for use in resource-limited settings

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Abstract

HIV testing has rapidly expanded worldwide, but proficiency testing (PT) programs to monitor and improve the quality of testing are often lacking in resource-limited settings (RLS). Traditional PT programs and quality control reagents use serum or plasma specimens requiring stringent conditions for storage and transportation.

A novel, simple and easy to use approach, based on dried tube specimens (DTS), was developed that can help monitor the quality of HIV antibody testing in RLS. DTS were prepared by drying 20 μl of specimen overnight at room temperature. The addition of a green dye (0.1%) made the DTS pellets visible without affecting the test results. Before testing, the DTS were rehydrated with 200 μl of PBS–Tween buffer. A panel of 303 DTS samples (135 HIV positive and 168 HIV negative) was evaluated with two rapid tests. Sensitivity and specificity with the Determine HIV-1/2 test were 99.3% and 99.4%, respectively, and with OraQuick were 98.5% and 100%, respectively. Stability studies showed that HIV-specific antibodies in the DTS specimens were stable at 4 °C and 25 °C for 4 weeks, with only marginal decline at 37 °C and 45 °C over 4 weeks. The DTS-based PT program was piloted successfully in 24 testing sites in Kenya.

Results demonstrate that the DTS is a simple to use, practical method to prepare and distribute PT panels and quality control specimens to monitor HIV testing practices in RLS.

Introduction

The increased commitment and resources from the U.S. President's Emergency Plan for AIDS Relief (PEPFAR), the Global Fund for AIDS, Tuberculosis, and Malaria (GFATM) and other major initiatives have resulted in a rapid expansion of testing for human immunodeficiency virus (HIV) in order to meet the prevention, care and treatment goals in many resource-limited countries (Jereni and Muula, 2008, Plate, 2007). HIV testing sites include national and regional laboratories, blood donation centers, antenatal clinics (mother–child health facilities), primary health centers, facility-based and stand-alone counseling and testing centers and mobile facilities. The majority of HIV testing in resource-limited settings is dependent on rapid tests performed by trained health-care professionals or lay counselors working in diverse and often non-laboratory settings, resulting in an expanded need to monitor the quality of testing procedures and ensure the accuracy of the results.

External quality assurance (EQA) is essential to ensure the accuracy of diagnostic testing. Key components of EQA are (a) proficiency testing (PT), (b) periodic retesting of a subset of specimens in a qualified laboratory and (c) site visits/audits by external experts. PT programs have been shown to be very effective in improving the quality of testing for various diseases and analytes (Chalermchan et al., 2007, Goguel, 1991, Hannon et al., 1989, Hofherr et al., 1992, Jackson et al., 1993, Peddecord et al., 1992, Polesky and Hanson, 1990, Reichelderfer and Jackson, 1994, Rickman et al., 1993, Schalla et al., 1990, Schwartz et al., 1988, Schweiger et al., 1997, Yen-Lieberman et al., 1996). However, they are either limited in coverage or lacking altogether in most developing countries, where the burden of the diseases is high and laboratory infrastructure is limited.

Several factors account for the limited EQA programs in developing countries. In countries where retesting is the primary means of monitoring the quality of HIV serologic testing, the approach is expensive, time consuming and logistically challenging in decentralized settings. Site visits to thousands of testing sites require a large number of trained personnel and resources as well as subsequent follow-up to ensure corrective actions have been taken. PT programs using liquid serum or plasma specimens are limited to laboratories or sites that are easily accessible and do not include thousands of rapid testing sites. Moreover, liquid specimens require a cold chain, which is expensive and difficult to maintain across the country.

To address the above challenges, a new, cold-chain independent approach is described here for PT program or for preparation of quality control specimens. Serum or plasma specimens, prepared as dried tube specimens (DTS), are stable for at least a month at temperatures encountered in many countries and can be used to prepare panels for PT or as quality control reagents.

Section snippets

Serum or plasma specimens

Initial evaluation and optimization of DTS and stability studies were performed using a well-characterized panel of 10 specimens (4 HIV-1 antibody positive and 6 HIV negative) routinely used in our laboratory. Following optimization, comparative study of DTS and liquid specimens was performed using a diverse panel of specimens (N = 303, 135 HIV positive and 168 HIV negative). These specimens were obtained from South Africa, Cameroon, Ivory Coast, Kenya and the United States. All specimens were

Optimal volume for DTS preparation

The various amounts (10 μl, 20 μl, 30 μl, 40 μl and 50 μl) of plasma specimens were allowed to dry at room temperature. The tubes with 10 μl and 20 μl dried overnight, but those with 30 μl or greater volume required 2–3 days to dry. Following rehydration, DTS preparations gave results consistent with expected results for the 10-member panel with Determine and OraQuick rapid tests, irrespective of the volume used. Volume of 20 μl was the preferred, optimal volume for DTS preparation since it dried

Discussion

HIV testing is the key entry point for prevention, counseling and service delivery and has expanded rapidly in the last 5 years in resource-limited settings. Access to testing at thousands of counseling and testing sites and task shifting, with testing performed by counselors, nurses and other health-care workers without formal training in the laboratory, provide a challenge to PT and the overall quality management system. In concert with training in rapid testing, assuring the continued

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