Stability of plasma human immunodeficiency virus load in VACUTAINER PPT plasma preparation tubes during overnight shipment

Effect of sample management on quantitative HIV-1 viral load measurement at Saint Paul’s Hospital Millennium Medical College, Addis Ababa, Ethiopia

Purpose

This study was meant to determine the effect of time to plasma separation, storage duration, freeze-thawing cycle and dilution proportion on the HIV-1 viral load level.

Methods

Experimental study design was employed by collecting 10mL whole blood samples into two EDTA tubes from 88 eligible HIV infected patients at St Paul’s Hospital Millennium Medical College. The viral load test was done using Abbott m2000sp/rt analyzer. Data was entered into Microsoft excel and analyzed by SPSS version 20. Repeated measure analysis of variance was used to compare HIV RNA viral load mean difference between different time to plasma separation, storage, freeze-thawing cycles and dilution levels. Post-hoc analysis was employed to locate the place of significant differences. P value less than 0.05 was used to declare statistical significance while viral RNA level of 0.5 log copies/ml was used to determine clinical significance.

Results

There was significant HIV-1 RNA viral load log mean difference between plasma separation time at 6 hours (hrs) and 24hrs (p<0.001). There was also significant HIV-1 RNA viral load log mean difference between plasma tested within 6hrs and those stored at 2–8°C for 15 days (p = 0.006), and between plasma stored at 2–8°C for 6 days versus 15 days (p<0.001). There was significant log mean difference between plasma that was exposed to fourth cycle of freeze-thawing after storage at -20°C when compared with plasma tested within 6hrs (p = 0.013).

Conclusion

Plasma separated at 24hrs, stored at 2–8°C for 15 days or freeze-thawed for four cycles had significant effect on HIV viral load level. However, the differences were not clinically significant at a cut-off viral load level of 0.5 log copies/ml. Avoiding delays to plasma separation beyond 24 hrs, storing at 2–8°C for 15 days and freeze-thawing for no more than 4 cycles is recommended to improve the result quality.

Systematic review of the accuracy of plasma preparation tubes for HIV viral load testing

Expanding access to HIV viral load testing is essential to improving the care and treatment of people living with HIV/AIDS and ending the AIDS epidemic. Though significant investments have been made in the past five years, many high burden, low resource countries continue to have viral load access rates below 50%. Plasma preparation tubes (PPTs) can simplify storage, transport, and preparation of plasma used for viral load testing. A systematic review was conducted to evaluate the accuracy of plasma preparation tubes for HIV viral load testing. Study results regarding the accuracy of PPT viral load measurements across various storage and transportation conditions were examined. The quality of evidence was evaluated using GRADE and QUADAS-2 criteria. The review identified 16 studies using PPTs with data from 6,141 individuals from 1995 to 2014. Overall the quality of evidence was rated as moderate, with unclear applicability for studies evaluating viral load assays that are no longer commercially available. Significantly elevated viral load results (>0.3 log copies/ml difference) have been observed with PPTs; however, when manufacturer handling instructions are followed, when plasma is aliquoted into a secondary tube, or when PPTs are centrifuged prior to testing, PPT results only differed from standard EDTA plasma testing using commercially available viral load assays by a range on average of -0.03 to +0.08 log copies/ml across studies. Although spuriously elevated viral load results have been observed with PPTs, following proper sample handing techniques have been shown to provide accurate results. PPTs, therefore, provide a high quality alternative specimen type for countries seeking solutions to infrastructure and specimen transportation challenges in an effort to scale-up viral load testing and achieve 90-90-90 targets.

Heterogeneous growth bent-cable models for time-to-event and longitudinal data: application to AIDS studies

The major limitations of growth curve mixture models for HIV/AIDS data are the usual assumptions of normality and monophasic curves within latent classes. This article addresses these limitations by using non-normal skewed distributions and multiphasic patterns for outcomes of prospective studies. For such outcomes, new skew-t (ST) distributions are proposed for modeling heterogeneous growth trajectories, which exhibit not abrupt but gradual multiphasic changes from a declining trend to an increasing trend over time. We assess these clinically important features of longitudinal HIV/AIDS data using the bent-cable framework within a context of a joint modeling of time-to-event process and response process. A real dataset from an AIDS clinical study is used to illustrate the proposed methods.

Joint two-part Tobit models for longitudinal and time-to-event data

In this article, we show how Tobit models can address problems of identifying characteristics of subjects having left-censored outcomes in the context of developing a method for jointly analyzing time-to-event and longitudinal data. There are some methods for handling these types of data separately, but they may not be appropriate when time to event is dependent on the longitudinal outcome, and a substantial portion of values are reported to be below the limits of detection. An alternative approach is to develop a joint model for the time-to-event outcome and a two-part longitudinal outcome, linking them through random effects. This proposed approach is implemented to assess the association between the risk of decline of CD4/CD8 ratio and rates of change in viral load, along with discriminating between patients who are potentially progressors to AIDS from patients who do not. We develop a fully Bayesian approach for fitting joint two-part Tobit models and illustrate the proposed methods on simulated and real data from an AIDS clinical study.

Joint bent-cable Tobit models for longitudinal and time-to-event data

In this article, we show how to estimate a transition period for the evolvement of drug resistance to antiretroviral (ARV) drug or other related treatments in the framework of developing a Bayesian method for jointly analyzing time-to-event and longitudinal data. For HIV/AIDS longitudinal data, developmental trajectories of viral loads tend to show a gradual change from a declining trend after initiation of treatment to an increasing trend without an abrupt change. Such characteristics of trajectories are also associated with a time-to-event process. To assess these clinically important features, we develop a joint bent-cable Tobit model for the time-to-event and left-censored response variable with skewness and phasic developments. Random effects are used to determine the stochastic dependence between the time-to-event process and response process. The proposed method is illustrated using real data from an AIDS clinical study.

A robust HIV-1 viral load detection assay optimized for Indian sub type C specific strains and resource limiting setting

BACKGROUND

Human Immunodeficiency Virus Type 1 (HIV-1) viral load testing at regular intervals is an integral component of disease management in Acquired Immunodeficiency Syndrome (AIDS) patients. The need in countries like India is therefore an assay that is not only economical but efficient and highly specific for HIV-1 sub type C virus. This study reports a SYBR Green-based HIV-1 real time PCR assay for viral load testing and is designed for enhanced specificity towards HIV-1 sub type C viruses prevalent in India.

RESULTS

Linear regression of the observed and reference concentration of standards used in this study generated a correlation coefficient of 0.998 (p<0.001). Lower limit of detection of the test protocol was 50 copies/ml of plasma. The assay demonstrated 100% specificity when tested with negative control sera. The Spearman coefficient of the reported assay with an US-FDA approved, Taqman probe-based commercial kit was found to be 0.997. No significant difference in viral load was detected when the SYBR Green based assay was used to test infected plasma stored at -20°C and room temperature for 7 days respectively (Wilcoxon signed rank test, p=0.105). In a comparative study on 90 pretested HIV-1 positive samples with viral loads ranging from 5,000-25,000 HIV-1 RNA copies/ml and between two commercial assays it was found that the later failed to amplify in 13.33% and 10% samples respectively while in 7.77% and 4.44% samples the copy number values were reduced by >0.5 log value, a figure that is considered clinically significant by physicians.

CONCLUSION

The HIV-1 viral load assay reported in this study was found to be robust, reliable, economical and effective in resource limited settings such as those existing in India. PCR probes specially designed from HIV-1 Subtype C-specific nucleotide sequences originating from India imparted specificity towards such isolates and demonstrated superior results when compared to two similar commercial assays widely used in India.

Evaluation of effect of specimen-handling parameters for plasma preparation tubes on viral load measurements obtained by using the Abbott RealTime HIV-1 load assay

HIV-1 viral load testing is essential to the management of HIV-1-infected patients, and proper specimen handling ensures accurate viral load (VL) results. This study was performed to (i) evaluate the effect of freezing plasma in situ in BD Vacutainer plasma preparation tubes (PPT) on the accuracy of HIV-1 viral load results using the Abbott RealTime HIV-1 assay and (ii) evaluate the effect of whole-blood storage in the PPT for 6 h at room temperature prior to centrifugation (PPT6H) rather than 2 h as specified in the PPT product insert. Of the 64 HIV-positive subjects evaluated, 29 had average viral load counts of >40 copies/ml in at least one of the tubes tested and 35 subjects had a result of either "undetected target" or "below the limit of quantification" (LOQ) for all or some of the tubes regardless of handling condition. For the 29 subjects with VLs that were >LOQ, the mean biases between plasma from Vacutainer K(2)EDTA tubes and plasma frozen in situ in PPT and between K(2)EDTA tube plasma and plasma from PPT6H (log(10) copies/ml) were 0.005 and -0.001, respectively, and r(2) was >0.92 for all correlations. We conclude that VLs determined from plasma frozen in situ in PPT are equivalent to VLs in K(2)EDTA tube plasma and can be used for accurate quantification of HIV-1 RNA in the Abbott RealTime HIV-1 assay. Furthermore specimens collected in PPT can be stored for 6 h at room temperature with no effect on viral load results as measured by the Abbott RealTime HIV-1 assay.

Overestimation of human immunodeficiency virus type 1 load caused by the presence of cells in plasma from plasma preparation tubes

The human immunodeficiency virus type 1 (HIV-1) load is an important marker of disease progression and treatment efficacy in patients with HIV-1 infection. In recent years, an increase in the number of samples with detectable HIV-1 RNA has been reported among patients with previously suppressed viral loads, affecting clinical patient care and leading to repeat measurements of viral load and drug resistance. This rise seems to have coincided with the increased use of plasma preparation tubes (PPTs) for sample collection, and we have aimed to explain why PPTs might yield elevated HIV-1 RNA levels. The impacts of different sample-processing procedures on HIV-1 RNA levels were compared retrospectively. Prospectively, the presence of different cells and cell-associated HIV-1 nucleic acids in paired plasma samples from PPTs centrifuged before (PPT1) and after (PPT2) transportation to the laboratory was compared. A retrospective analysis of 4,049 patient samples with <1,000 HIV-1 RNA copies/ml showed elevated HIV-1 RNA levels in plasma from PPT1 compared with the levels from PPT2 and standard EDTA-containing tubes. Prospective data revealed cell-associated HIV-1 nucleic acids and abundant blood cells in plasma from PPT1 but not from the corresponding PPT2. The levels of HIV-1 RNA correlated with the lymphocyte counts in plasma in PPT1. Cells could be removed by the recentrifugation of PPT1 before analysis. In conclusion, the transportation of PPTs after centrifugation may render cells in the plasma fraction containing cell-associated HIV-1 nucleic acids that contribute significantly to the HIV-1 RNA copy numbers in patients with low viral loads.

A nonparametric likelihood test for detecting discordance between two measurements with application to censored viral load determinations

Patient management frequently involves quantitative evaluation of a patient's attributes. For example, in HIV studies, a high viral load can be a trigger to initiate or modify an antiretroviral therapy. At times, a new method of evaluation may substitute for an established one, provided that the new method does not result in different clinical decisions compared with the old method. Traditional measures of agreement between the two methods are inadequate for deciding if a new method can replace the old. Especially, when the data are censored by a detection limit, estimates of agreement can be biased unless the distribution for the censored data is correctly specified; this is usually not feasible in practice. We propose a nonparametric likelihood test that seamlessly handles censored data. We further show that the proposed test is a generalization of the test on nominal measurement concordance to continuous measurement. An exact permutation procedure is proposed for implementing the test. Our application is an HIV study to determine whether one method of processing plasma samples can safely substitute for the other. The plasma samples are used to determine viral load and a large portion of data are left censored due to a lower detection limit.

HIV-1 and HCV viral load cost models for bDNA: 440 Molecular System versus real-time PCR AmpliPrep/TaqMan test

Comparative cost models were developed to assess cost-per-reportable result and annual costs for HIV-1 and HCV bDNA and AmpliPrep/TaqMan Test (PCR). Model cost components included kit, disposables, platform and related equipment, equipment service plan, equipment maintenance, equipment footprint, waste and labor. Model assessment was most cost-effective when run by bDNA with 36 or more clinical samples and PCR with 30 or fewer clinical samples. Lower costs are attained with maximum samples (84-168) run daily. Highest cost contributors include kit, platform and PCR proprietary disposables. Understanding component costs and the most economic use of HIV-1 and HCV viral load will aid in attaining lowest costs through selection of the appropriate assay and effective negotiations.

Elevation of viral load by PCR and use of plasma preparation tubes for quantification of human immunodeficiency virus type 1

HIV-1 viral load testing from 51 patients was compared in plasma samples simultaneously processed and stored in primary Vacutainer plasma preparation tubes (PPTs) and PPT sample aliquots transferred in secondary tubes before freezing, using RT-PCR quantification with an ultrasensitive method (the Roche AMPLICOR HIV-1 MONITOR). We concluded that freezing the primary sample in the PPT collection tube can artificially elevate the HIV-1 viral load. We therefore store samples as frozen aliquots in a second tube.

Differential effect of blood collection tubes on total free fatty acids (FFA) and total triiodothyronine (TT3) concentration: a model for studying interference from tube constituents

BACKGROUND

Besides total triiodothyronine (TT3), total free fatty acids (FFA) concentrations were higher with serum separator tube (SST) than Vacuette tubes.

METHODS

The effects of surfactant, rubber stopper, and separator gel from various tubes were investigated on FFA, beta-hydroxybutyrate (beta-HB), and TT3 with 8 different tube types in blood specimens of apparently healthy volunteers.

RESULTS

Compared to Vacuette tubes, serum FFA and TT3 concentrations were significantly higher in SST than glass tubes. Reformulated SST eliminated the increase in TT3 but not FFA. No significant difference was observed for beta-HB concentration among tube types. Surfactant and rubber stoppers from the different tube types significantly increased TT3 but not FFA and beta-HB concentrations. Agitation of whole blood but not serum or plasma specimens with separator gel from SST, reformulated SST and plasma preparation tube (PPT) tubes compared to Vacuette tubes gave higher FFA but not beta-HB levels.

CONCLUSIONS

Unidentified component(s) from the separator gel in SST, reformulated SST and PPT tubes cause falsely high FFA concentration. In contrast to TT3, falsely high FFA results require exposure of whole blood and not serum to tube constituent(s). The approach employed here may serve as a model for assessing interference(s) from tube constituent(s).

HIV-1 load quantitation: a 17-year perspective

During the past decade and a half, quantitation of plasma-associated human immunodeficiency virus type 1 (HIV-1) RNA level, or HIV-1 load, has been validated in clinical practice and clinical trials as an important surrogate marker of HIV-1 disease progression and of the potency and durability of antiretroviral regimens. This review highlights some of the history, accomplishments, and impact of Tom Merigan's laboratory on the use of HIV-1 load as a marker, as well as on updating technologies for determining HIV-1 load, their performance, interpretation of the results, and their use in clinical practice.

Transient Viremia in HIV-Infected Patients and Use of Plasma Preparation Tubes

Using plasma preparation tubes for the collection and storage of plasma resulted in factitious, low-level human immunodeficiency virus type 1 (HIV-1) viremia among patients receiving highly active antiretroviral therapy who incurred unnecessary additional clinic visits, laboratory testing, and medication changes. We caution clinicians against the routine use of plasma preparation tubes for collection of blood samples for HIV-1 level 1 quantification.

Discordance between viral loads determined by Roche COBAS AMPLICOR human immunodeficiency virus type 1 monitor (version 1.5) Standard and ultrasensitive assays caused by freezing patient plasma in centrifuged becton-dickinson vacutainer brand plasma preparation tubes

The Roche COBAS AMPLICOR human immunodeficiency virus type 1 (HIV-1) Monitor (version 1.5) standard and ultrasensitive viral load assays often gave discordant results, with viral loads from the standard assay exceeding those from the ultrasensitive assay by more than 0.5 log(10) for approximately 20% of specimens received. We began studies to determine the extent, magnitude, and reproducibility of the discordance between the assays and to discover and eliminate the cause of this discordance. Until then, we revised our standard operating procedure to include both standard and ultrasensitive testing on all specimens submitted for viral load determinations. Discordant results usually recurred on retesting. They were most prevalent for specimens with ultrasensitive viral loads of <1,000 and rare for specimens with viral loads of >10,000. Often, standard assay results exceeded those of the ultrasensitive assay by 50- to 100-fold. At higher viral loads, the difference between the standard and ultrasensitive assays persisted, but the percent difference was smaller and rarely caused discordance. The proportion of discordant results was significantly higher in specimens from pediatric patients than in specimens from adults. The ultrasensitive viral load determinations generally agreed with the results of the B-DNA (Bayer) viral load assays. If the plasma was transferred from the centrifuged plasma preparation tubes before freezing, standard and ultrasensitive results were concordant with each other and with values determined on plasma from lavender-topped EDTA tubes.

Increased levels of HIV RNA detected in samples with viral loads close to the detection limit collected in Plasma Preparation Tubes (PPT)

BACKGROUND

The accurate and reliable quantification of HIV RNA is an essential part of the management of HIV infected individuals, and elucidation of factors that may affect HIV RNA measurements, such as the use of Vacutainer Plasma Preparation Tubes (PPT), is crucial.

OBJECTIVES

The objective of this study was to determine if plasma samples with viral loads close to the lower limit of the dynamic range of the assay collected in PPT tubes had increased levels of HIV RNA as compared to samples collected in standard EDTA tubes.

STUDY DESIGN

HIV RNA levels were compared in 112 paired plasma samples collected in PPT and standard EDTA tubes. All samples had been frozen prior to testing.

RESULTS

Discrepancies between PPT and EDTA tubes did not occur for samples with high viral loads. However, in samples with viral loads close to the lower limit of the dynamic range, levels of HIV RNA detected were higher in a large proportion of PPT as compared to the corresponding EDTA plasma samples. Forty percent of plasma pairs had no detectable HIV RNA in the EDTA aliquot, but had low levels of HIV RNA in the corresponding PPT aliquot.

CONCLUSIONS

This prospective study underlines the need for cautious interpretation of small transient viral load changes in samples with values close to the detection limit.

Evaluation of the VACUTAINER PPT Plasma Preparation Tube for use with the Bayer VERSANT assay for quantification of human immunodeficiency virus type 1 RNA

Separation and storage of plasma within 2 h of phlebotomy is required for the VACUTAINER PPT Plasma Preparation Tube (PPT) versus 4 h for the predecessor VACUTAINER EDTA tube for human immunodeficiency virus type 1 (HIV-1) viral load (HIVL) testing by the VERSANT HIV-1 RNA 3.0 assay (branched DNA). The 2-h limit for PPT imposes time constraints for handling and transporting to the testing laboratory. This study compares HIVL reproducibility from matched blood in EDTA tubes and PPTs and between PPT pairs following processing within 4 h of phlebotomy, stability of plasma HIV-1 RNA at 24- and 72-h room temperature storage in the tube, and comparative labor and supply requirements. Blood from 159 patients was collected in paired tubes (EDTA/PPT or PPT/PPT): 86 paired EDTA tubes and PPTs were processed 4 h following phlebotomy and their HIVLs were compared, 42 paired PPT/PPT pairs were analyzed for intertube HIVL reproducibility, and 31 PPT/PPT pairs were analyzed for HIV-1 RNA stability by HIVL. Labor and supply requirements were compared between PPT and EDTA tubes. PPTs produce results equivalent to standard EDTA tube results when processed 4 h after phlebotomy. PPT intertube analyte results are reproducible. An average decrease of 13% and 37% in HIVL was observed in PPT plasma after 24 and 72 h of room temperature storage, respectively; thus, plasma can be stored at room temperature up to 24 h in the original tube. PPTs offer labor and supply savings over EDTA tubes.