HIV-1 viral load measurement in venous blood and fingerprick blood using Abbott RealTime HIV-1 DBS assay.

BACKGROUND: HIV RNA suppression is a key indicator for monitoring success of antiretroviral therapy. From a logistical perspective, viral load (VL) testing using Dried Blood Spots (DBS) is a promising alternative to plasma based VL testing in resource-limited settings. OBJECTIVES: To evaluate the analytical and clinical performance of the Abbott RealTime HIV-1 assay using a fully automated one-spot DBS sample protocol. STUDY DESIGN: Limit of detection (LOD), linearity, lower limit of quantitation (LLQ), upper limit of quantitation (ULQ), and precision were determined using serial dilutions of HIV-1 Virology Quality Assurance stock (VQA Rush University), or HIV-1-containing armored RNA, made in venous blood. To evaluate correlation, bias, and agreement, 497 HIV-1 positive adult clinical samples were collected from Ivory Coast, Uganda and South Africa. For each HIV-1 participant, DBS-fingerprick, DBS-venous and plasma sample results were compared. Correlation and bias values were obtained. The sensitivity and specificity were analyzed at a threshold of 1000 HIV-1 copies/mL generated using the standard plasma protocol. RESULTS: The Abbott HIV-1 DBS protocol had an LOD of 839 copies/mL, a linear range from 500 to 1×107 copies/mL, an LLQ of 839 copies/mL, a ULQ of 1×107 copies/mL, and an inter-assay SD of ≤0.30 log copies/mL for all tested levels within this range. With clinical samples, the correlation coefficient (r value) was 0.896 between DBS-fingerprick and plasma and 0.901 between DBS-venous and plasma, and the bias was -0.07 log copies/mL between DBS-fingerprick and plasma and -0.02 log copies/mL between DBS-venous and plasma. The sensitivity of DBS-fingerprick and DBS-venous was 93%, while the specificity of both DBS methods was 95%. CONCLUSION: The results demonstrated that the Abbott RealTime HIV-1 assay with DBS sample protocol is highly sensitive, specific and precise across a wide dynamic range and correlates well with plasma values. The Abbott RealTime HIV-1 assay with DBS sample protocol provides an alternative sample collection and transfer option in resource-limited settings and expands the utility of a viral load test to monitor HIV-1 ART treatment for infected patients.

Analytical and clinical performance characteristics of the Abbott RealTime MTB RIF/INH Resistance, an assay for the detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis in pulmonary specimens.

Clinical management of drug-resistant tuberculosis patients continues to present significant challenges to global health. To tackle these challenges, the Abbott RealTime MTB RIF/INH Resistance assay was developed to accelerate the diagnosis of rifampicin and/or isoniazid resistant tuberculosis to within a day. This article summarizes the performance of the Abbott RealTime MTB RIF/INH Resistance assay; including reliability, analytical sensitivity, and clinical sensitivity/specificity as compared to Cepheid GeneXpert MTB/RIF version 1.0 and Hain MTBDRplus version 2.0. The limit of detection (LOD) of the Abbott RealTime MTB RIF/INH Resistance assay was determined to be 32 colony forming units/milliliter (cfu/mL) using the Mycobacterium tuberculosis (MTB) strain H37Rv cell line. For rifampicin resistance detection, the Abbott RealTime MTB RIF/INH Resistance assay demonstrated statistically equivalent clinical sensitivity and specificity as compared to Cepheid GeneXpert MTB/RIF. For isoniazid resistance detection, the assay demonstrated statistically equivalent clinical sensitivity and specificity as compared to Hain MTBDRplus. The performance data presented herein demonstrate that the Abbott RealTime MTB RIF/INH Resistance assay is a sensitive, robust, and reliable test for realtime simultaneous detection of first line anti-tuberculosis antibiotics rifampicin and isoniazid in patient specimens.

Analytical and clinical performance of Abbott RealTime MTB, an assay for detection of Mycobacterium tuberculosis in pulmonary specimens.

Nucleic acid amplification test (NAAT)-based assays provide fast and sensitive results compared to conventional TB tests. The performance of the new Abbott Molecular MTB assay for the qualitative detection of MTB complex using the automated m2000™ system or manual sample preparation is summarized in this paper. The assay detects eight MTB complex subspecies. The observed limit of detection (LOD) when used to test an MTB H37Rv panel was 2.45 colony forming units (cfu)/mL, while the claimed assay LOD with this MTB strain is 17 cfu/mL. No cross reactivity, or carryover were observed in the study. The clinical sensitivity of the assay was 93% overall; 99% in smear positive, culture positive specimens, and 81% in smear negative, culture positive samples. The clinical specificity was 97%. The inhibition rate in the study was 0.34%. The data suggest that Abbott RealTime MTB is a reliable, robust and sensitive assay for the molecular detection of MTB.

Performance attributes of the LCx HCV RNA quantitative assay.

The LCx HCV RNA quantitative assay (Abbott Laboratories, North Chicago, IL) is designed to use competitive reverse transcriptase-polymerase chain reaction (RT-PCR) and microparticle enzyme immunoassay (MEIA), in combination with a modified Qiagen sample preparation method, to measure the level of hepatitis C virus (HCV) in human plasma and serum. The assay provides quantitative results in international units (IU) of HCV RNA/ml, in copies of HCV RNA/ml, or their log (base 10) equivalents. A conversion study determined that 1IU equals 4.3 copies. The LCx HCV assay detected HCV RNA transcripts representative of genotypes 1-6 with near equal efficiency. The assay did not cross-react with high concentrations of 21 potentially cross-reactive microorganisms or with 100 HCV-negative specimens. The lower limit of detection was demonstrated to be 23IU/ml. The LCx assay had similar sensitivity to the Roche Amplicor HCV (version 2.0) qualitative assay when used to test panels containing 6, 12, 23, and 47IU/ml. The assay linear range was shown to extend from 23 to 2.3millionIU/ml. The intra-assay standard deviation (S.D.) was < or =0.066 logIU/ml for the four HCV positive samples tested, while for the same samples the observed inter-assay S.D. was < or =0.075 logIU/ml. The overall mean assay quantitation value for seven HCV-positive WHO-standardized Acrometrix NAP linearity panel members was within 0.06 logIU/ml of the mean assigned value. The assay was demonstrated to correlate acceptably against the Roche Amplicor HCV monitor test (version 2.0). These data suggest that the assay is standardized appropriately against the WHO standard across its linear range and can be used for quantitation of HCV. In addition, with a sensitivity of 23IU/ml, the assay can be used to determine if post-therapy viral clearance has occurred.