3rd WHO Research Articles

Collaborative study for the calibration of a replacement International Standard for tetanus toxoid for use in flocculation test

Here we report the results of a study to establish a replacement WHO International Standard (IS) for tetanus toxoid for use in flocculation test. The standard was calibrated in flocculation units (Lf) against the 2nd IS using the Ramon flocculation method. At its 70th meeting in October 2019, WHO ECBS established the material (coded 16/302) as the 3rd WHO IS, with an assigned value of 970 Lf/ampoule from the results of seventeen laboratories across ten different countries.The study also provided an opportunity to assess the use of alternative methods for measuring Lf. Participants were asked to use an in-house Enzyme Linked Immunosorbent Assay (ELISA) developed at NIBSC, or other suitable in-house methods, to determine ELISA-specific Lf values (Lf-eq units are specific only for pre-calibration of antitoxin in the flocculation test) of 16/302 to compare to those of the flocculation test. Nine laboratories participated by performing the NIBSC ELISA, one laboratory performed flocculation by laser light-scattering following an in-house protocol, and three laboratories performed ELISA following in-house protocols. The results intimate that these alternative methods could be useful for monitoring consistency of production at different stages of vaccine manufacturing.

World variation in head circumference for children from birth to 5 years and a comparison with the WHO standards

ObjectiveA recent review reported that the WHO 2006 growth standards reflect a smaller head circumference at 24 months than seen in 18 countries. Whether this happens in early infancy and...

To study the effect of microbial contamination in semen and its effect on male infertility

According to the 3rd WHO methods, normal sperm morphology has been considered to be directly related with the fertilization process and pregnancy. The quality of semen such as sperm morphology, count, and motility has been reduced due to abnormalities in male thus, causing infertility. A considerable factor responsible for infertility among male partners may be as a result of microbial contamination. Semen may contain contamination while collecting sample. However, there are some sperm preparation techniques that can be used for the removal of contamination in semen such as; swim up, density gradient, simple wash, discontinuous density gradient. The main objective of this study is to find out the presence of infections and microbial contamination. This study will compare sperm count and sperm motility of patient’s semen sample with numbers of debris/ present infectious agent. Microbiological assay of semen sample will be performed. Also, various infectious agents causing infertility will be evaluated and studied. Semen analysis, semen preparation by density gradient, semen culture were carried out to look into the effect of microbial contamination on semen sample of infertile men.

Onasemnogene abeparvovec for presymptomatic infants with three copies of SMN2 at risk for spinal muscular atrophy: the Phase III SPR1NT trial

Most children with biallelic SMN1 deletions and three SMN2 copies develop spinal muscular atrophy (SMA) type 2. SPR1NT (NCT03505099), a Phase III, multicenter, single-arm trial, investigated the efficacy and safety of onasemnogene abeparvovec for presymptomatic children with biallelic SMN1 mutations treated within six postnatal weeks. Of 15 children with three SMN2 copies treated before symptom onset, all stood independently before 24 months (P < 0.0001; 14 within normal developmental window), and 14 walked independently (P < 0.0001; 11 within normal developmental window). All survived without permanent ventilation at 14 months; ten (67%) maintained body weight (≥3rd WHO percentile) without feeding support through 24 months; and none required nutritional or respiratory support. No serious adverse events were considered treatment-related by the investigator. Onasemnogene abeparvovec was effective and well-tolerated for presymptomatic infants at risk of SMA type 2, underscoring the urgency of early identification and intervention.

The international biodosimetry capacity, capabilities, needs and challenges: The 3rd WHO BioDoseNet survey results

In 2008 the World Health Organization established an international network of biodosimetry laboratories, the BioDoseNet. The goal of this network is to support international cooperation and capacity building in the area of biodosimetry, including harmonisation of protocols and techniques to enable them to provide mutual assistance during a mass casualty event. Since its inception, the evolution, success and needs of the network have been monitored by multiple surveys conducted approximately every five years. The third such survey was conducted in 2021, now allowing trends capabilities and capacities of the members of the network to be seen over time. The results of the survey offer an overview of the global status of cytogenetic biodosimetry service and demonstrate how the BioDoseNet has brought together laboratories from around the world and strengthened international biodosimetry.

Samples spiked with pituitary-derived thyroid-stimulating hormone may disguise the extent of differences between thyroid-stimulating hormone assays.

A large discordance in the diagnosis and potential management of hypothyroidism using Abbott and Roche thyroid assays has been reported recently. The difference in Abbott and Roche thyroid-stimulating hormone (TSH) results in these studies was larger than anticipated from the external quality assessment (EQA) reports. Abbott and Roche TSH method means in UK NEQAS for thyroid hormones distributions 430 to 454 were compared against the amount of TSH spiked. A TSH deplete serum pool was spiked with various concentrations of pooled high TSH serum and 3rd WHO International Standard for TSH (WHO-IS). Four serum pools with TSH close to clinical decision limits were spiked with two concentrations of WHO-IS. On review of EQA data, median (IQR) Roche: Abbott TSH ratio was lower (p < 0.001) in 48 pools spiked with TSH (1.11 (1.07-1.16)) compared to 41 pools not spiked (1.29 (1.25-1.31)) and the decrease was proportionate to the contribution of spiked TSH to total TSH in the samples (ρ=-0.908, p < 0.001). In spiking experiments, the relationship of Roche and Abbott TSH was different in TSH deplete pool spiked with WHO-IS (RocheTSH=1.13*AbbottTSH-0.52) and high TSH serum (RocheTSH=1.43*AbbottTSH-0.50), respectively. The Roche: Abbott TSH ratio decreased and the method agreement improved on spiking serum pools with WHO-IS. Abbott and Roche TSH assays are not in harmony in human serum samples but the agreement was better in samples spiked with WHO-IS which contains pituitary-derived TSH. Use of pituitary-derived TSH spiked samples, such as provided by EQA schemes, may mask clinically significant between-assay differences.

Comparison of CaptiaTM Measles IgG Assay with Vidas® Measles IgG Assay for determination of immune protection status against measles virus

BackgroundCorrelation of the assay cut-off values for CaptiaTM Measles IgG and the Vidas® Measles IgG assays with the World Health Organization recommended immunoprotective level of ≥120 mIU/mL is not stated by the manufacturers. Lack of such information may affect interpretation of immune protection (IP) for measles. ObjectiveThe aim of this study was to compare the relative performance of the CaptiaTM Measles IgG assay and the Vidas® Measles IgG assay for determination of IP against measles virus. Study designCorrelation of the cut-off value of both assays with the immunoprotective level was determined with the 3rd WHO Measles IgG International Standard. One hundred clinical samples including frozen and fresh were tested with both assays. The positive percentage agreement (PPA) based on the manufacturers' interpretation and the WHO recommended immunoprotective level was compared. ResultsSamples tested positive by the CaptiaTM assay were at or above the immunoprotective level while those tested equivocal and positive by the Vidas® assay were immune protective. The overall PPA between both assays was 78.31 % (95 % CI = 67.91–86.61%). When Vidas® equivocal results were regarded as immunoprotective, the overall IP agreement was 96.39 % (95 % CI = 89.80–99.25 %). ConclusionsCaptiaTM assay was more sensitive than the Vidas® assay in determination of IP against measles virus. Testing of measles immunity with the Vidas® Measles IgG assay might underestimate the IP unless equivocal results were regarded as immunoprotective.

A pilot study on health risk assessment based on body loadings of PCBs of lactating mothers at Taizhou, China, the world's major site for recycling transformers

Our early study reported an extraordinarily high Estimated Daily Intake (EDI) of PCBs of lactating mothers from Taizhou, Zhejiang Province, China (based on a food consumption survey and food basket analysis). The EDI well exceeded the intake limit stipulated by FAO/WHO 70 pg TEQ/kg body weight (bw)/month. The present pilot study provided further information on PCBs body burden in lactating mothers of Taizhou. The total PCBs detected in human milk, placenta and hair samples of these lactating mothers were 363 ng/g lipid, 224 ng/g lipid, and 386 ng/g dry wt. Respectively, three times higher than those samples collected from the reference site (Lin'an). Compared with the previous reported values in the 3rd WHO coordinated study, Taizhou topped the list of 32 countries/regions with regards to WHO-PCB-TEQ values of milk samples, which could be attributed to the relatively higher level of PCB-126 derived from electronic waste. In addition, the corresponding EDI of PCBs of Taizhou mothers (12.9 pg WHO-PCB-TEQ/kg bw/day) and infants (438 pg WHO-PCB-TEQ/kg) were derived from individual congener levels in human milk. The results were also higher than the tolerable daily intakes recommended by WHO (1–4 pg WHO-TEQ/kg bw/day) by 3 and 110 times, for mothers and infants, respectively. A more intensive epidemiological study on the potential health effects of e-waste recycling activities affecting both workers and residents seems to be of top priority, based on findings of this pilot study.

A collaborative study to establish the 3rd WHO International Standard for hepatitis B virus for nucleic acid amplification techniques

Nucleic acid amplification techniques (NAT) are routinely used for clinical diagnostics and monitoring hepatitis B virus (HBV) infections, and are implemented on a voluntary basis for blood screening. A collaborative study was performed to evaluate a replacement WHO International Standard for HBV for the standardization of NAT. Two lyophilised HBV candidates were evaluated by 16 laboratories worldwide, alongside the existing HBV International Standard. The overall mean potency estimates for the candidate samples 1 and 2, relative to sample 3 (2nd HBV International Standard), from quantitative assays, were 5.93 and 5.98 log10 International Units (IU)/mL respectively. The variability in individual laboratory mean estimates for samples 1–3 for quantitative assays was ∼0.3 log10 IU/mL. The inter-laboratory variability for qualitative assays was higher. Accelerated thermal degradation studies indicate that both lyophilised candidates are stable and suitable for long-term use. Overall, the results suggested that both candidates were suitable as replacement International Standards. Sample 1 (NIBSC code 10/264) was established as the 3rd WHO International Standard for HBV for NAT with an assigned potency of 850,000 IU/mL (∼5.93 log10 IU/mL), when reconstituted in 0.5 mL of nuclease-free water. It is intended for the calibration (in IU) of secondary reference materials used in HBV NAT.

International collaborative study on the 3rd WHO International Standard for hepatitis B surface antigen

BackgroundThe WHO International Standard (IS) for hepatitis B surface antigen (HBsAg) is used to standardize HBsAg assays. Stocks of the 2nd IS for HBsAg are depleted. The proposal to establish its replacement was endorsed by WHO in 2012. ObjectivePreparation of a freeze-dried candidate 3rd IS (NIBSC 12/226); evaluation of its suitability in a WHO international collaborative study; calibration of its potency in International Units (IU). Study designThe 3rd IS is based on plasma-derived, purified, inactivated HBsAg from Vietnam. Qualitative and quantitative HBsAg assays were used to evaluate 12/226 alongside the 2nd IS and 1st IS. Blinded study samples included a duplicate of 12/226, a negative control and two diluted plasma samples representing hepatitis B virus (HBV) genotypes A and B. ResultsTwelve laboratories from 9 countries returned 22 data sets from 15 methods. The overall geometric mean potency of 12/226 is 47.3IU/mL (±13% CV) when compared to the 2nd IS with HBV subgenotype A2. The 3rd IS has HBV subgenotype B4 with a heterogeneous HBsAg subtype population of ayw1 and adw2. Some genotype-dependent effects on the inter-laboratory variability were observed but overall mean potencies were virtually identical irrespective of the IS used for calibration. Stability studies indicate that the candidate is stable for long-term use. Conclusions12/226 was established in October 2014 by the WHO Expert Committee on Biological Standardization as the 3rd IS for HBsAg with a potency of 47.3IU per ampoule maintaining the continuity in the standardization of HBsAg assays.

A significantly lower potency observed for the 3rd WHO International Standard for Parvovirus B19V DNA with the cobas TaqScreen DPX test.

In the context of the Official Medicines Control Laboratories plasma pool testing for Parvovirus B19 DNA, we use the cobas TaqScreen DPX test. When we re-evaluated this method using the 3rd B19 DNA WHO IS at the final concentration of 4 log IU/mL, we observed a titre lower than expected, i.e. 3.79 log IU/mL. Therefore, we further investigated the accuracy of the DPX test. The following B19V DNA materials were tested by using both the DPX test and an in-house real-time PCR: The 1st, 2nd and 3rd WHO ISs for B19V DNA The Non WHO B19V DNA Reference Material for NAT The Biological Reference Preparation B19 virus DNA for NAT testing, batch 1 . The DPX test showed a good accuracy for all B19V DNA materials with the exception of the 3rd WHO IS for B19V DNA. In fact, an underestimation of about 38% was observed for all dilutions of this standard with respect to the nominal titre. With the B19V in-house real-time PCR, all four materials proved to be well calibrated against the 1(st) WHO IS for B19V DNA, used as external standard curve. In this study, we demonstrated that the DPX test underestimates the B19V DNA content of the 3rd WHO IS for B19V DNA and that this is not due to an incorrect potency assigned to the standard but, most probably, to a mismatch between the primers/probe and the sequence of the target region in the 3rd WHO IS for B19V DNA.

Aptima HIV-1 Quant Dx—A fully automated assay for both diagnosis and quantification of HIV-1

BackgroundSeparate assays are available for diagnosis and viral load (VL) monitoring of HIV-1. Studies have shown that using a single test for both confirmatory diagnosis and VL increases linkage to care. ObjectiveTo validate a single assay for both diagnosis and VL monitoring of HIV-1 on the fully automated Panther platform. Study designValidate the assay by assessing specificity, sensitivity, subtype detection, seroconversion, reproducibility and linearity. Also assess diagnostic agreement with the Procleix® Ultrio Elite™ discriminatory assay (Procleix), and agreement of VL results (method comparison) with Ampliprep/COBAS TaqMan HIV-1 version 2.0 (CAP/CTM), using clinical samples. ResultsThe assay was specific (100%) and sensitive with a 95% limit of detection of 12 copies/mL with the 3rd WHO standards. Aptima detected HIV in seroconversion panels 6 and 11 days before p24 antigen and antibody tests, respectively. Diagnostic agreement with Procleix, was 100%. Regression analysis showed good agreement of VL results between Aptima and CAP/CTM with a slope of 1.02, intercept of 0.07, and correlation coefficient (R2) of 0.97. Aptima was more sensitive than CAP/CTM. Equivalent quantification was seen on testing clinical samples and isolates belonging to HIV group M, N, O and P and commercially available subtype panels. Assay results were linear (R2 0.9994) with standard deviation of <0.17 log copies across assay range. ConclusionsThe good specificity, sensitivity, precision, subtype performance and clinical agreement with other assays demonstrated by Aptima combined with the complete automation provided by the Panther platform makes Aptima a good candidate for both VL monitoring and diagnosis of HIV-1.

Strengthening the influenza vaccine virus selection and development process: Report of the 3rd WHO Informal Consultation for Improving Influenza Vaccine Virus Selection held at WHO headquarters, Geneva, Switzerland, 1–3 April 2014

Despite long-recognized challenges and constraints associated with their updating and manufacture, influenza vaccines remain at the heart of public health preparedness and response efforts against both seasonal and potentially pandemic influenza viruses.Globally coordinated virological and epidemiological surveillance is the foundation of the influenza vaccine virus selection and development process. Although national influenza surveillance and reporting capabilities are being strengthened and expanded, sustaining and building upon recent gains has become a major challenge.Strengthening the vaccine virus selection process additionally requires the continuation of initiatives to improve the timeliness and representativeness of influenza viruses shared by countries for detailed analysis by the WHO Global Influenza Surveillance and Response System (GISRS).Efforts are also continuing at the national, regional, and global levels to better understand the dynamics of influenza transmission in both temperate and tropical regions. Improved understanding of the degree of influenza seasonality in tropical countries of the world should allow for the strengthening of national vaccination policies and use of the most appropriate available vaccines.There remain a number of limitations and difficulties associated with the use of HAI assays for the antigenic characterization and selection of influenza vaccine viruses by WHOCCs. Current approaches to improving the situation include the more-optimal use of HAI and other assays; improved understanding of the data produced by neutralization assays; and increased standardization of serological testing methods.A number of new technologies and associated tools have the potential to revolutionize influenza surveillance and response activities. These include the increasingly routine use of whole genome next-generation sequencing and other high-throughput approaches. Such approaches could not only become key elements in outbreak investigations but could drive a new surveillance paradigm. However, despite the advances made, significant challenges will need to be addressed before next-generation technologies become routine, particularly in low-resource settings.Emerging approaches and techniques such as synthetic genomics, systems genetics, systems biology and mathematical modelling are capable of generating potentially huge volumes of highly complex and diverse datasets. Harnessing the currently theoretical benefits of such bioinformatics (“big data”) concepts for the influenza vaccine virus selection and development process will depend upon further advances in data generation, integration, analysis and dissemination.Over the last decade, growing awareness of influenza as an important global public health issue has been coupled to ever-increasing demands from the global community for more-equitable access to effective and affordable influenza vaccines. The current influenza vaccine landscape continues to be dominated by egg-based inactivated and live attenuated vaccines, with a small number of cell-based and recombinant vaccines. Successfully completing each step in the annual influenza vaccine manufacturing cycle will continue to rely upon timely and regular communication between the WHO GISRS, manufacturers and regulatory authorities.While the pipeline of influenza vaccines appears to be moving towards a variety of niche products in the near term, it is apparent that the ultimate aim remains the development of effective “universal” influenza vaccines that offer longer-lasting immunity against a broad range of influenza A subtypes.

Comparative performance of the new Aptima HIV-1 Quant Dx assay with three commercial PCR-based HIV-1 RNA quantitation assays

BackgroundQuantitative measurement of HIV-1 RNA levels in plasma (‘viral load’) plays a central role in clinical management. The choice of assay platform can influence results and treatment decisions. ObjectiveTo compare the analytical performance of the new TMA-based Hologic Aptima® HIV-1 Quant Dx assay with that of three PCR-based assays: Abbott RealTime HIV-1, Qiagen Artus® HI Virus-1 QS-RGQ, and Roche CAP/CTM HIV-1 Test v2. Study designAssay performance was evaluated using Acrometrix HIV-1 RNA Standard panels; the 3rd WHO HIV-1 RNA International Standard (12–500copies/ml; 6 dilutions; 9 replicates); and plasma samples from 191 HIV-positive patients. ResultsAptima showed high (>0.99) precision, accuracy and concordance with the Acrometrix Standards across a wide dynamic range (2.0–6.7 log10copies/ml). Variance caused up to 2.1 (Aptima), 1.7 (RealTime), 7.5 (Artus), and 1.9 (CAP/CTM) fold changes in the International Standard quantifications at 50–500copies/ml. HIV-1 RNA detection rates in plasma samples were 141/191 (74%), 119/191 (62%), 108/191 (57%), and 145/191 (76%) for Aptima, RealTime, Artus and CAP/CTM, respectively. For categorising samples either side of 50 copies/ml, Aptima had excellent agreement with RealTime (kappa 0.92; 95% CI 0.87–0.98); lowest agreement was with Artus (kappa 0.79; 95%CI 0.70–0.88). Aptima quantifications were mean 0.12 and 0.06 log10copies/ml higher compared with RealTime and CAP/CTM, respectively, and 0.05 log10copies/ml lower compared with Artus. Limits of agreement were narrowest when comparing Aptima to RealTime. ConclusionsThe new Aptima HIV assay is sensitive, precise, and accurate. HIV assays exhibit discordance at low HIV-1 RNA copy numbers.

Revaluating serum ferritin as a marker of body iron stores in the traceability era

Serum ferritin is used for diagnosing iron-related disorders. However, most studies validating this application were performed before the introduction of the 2nd and 3rd WHO International Standards (ISs) to harmonize assay results. We revised the available literature to evaluate if consolidated clinical applications of ferritin and recommended cut-offs have been validated using ISs calibrated assays. All Medline retrieved reviews and individual studies performed since ISs availability were selected and analyzed according to predefined criteria. Concerning ferritin and iron deficiency (ID), only one review, including studies published before 1988, met established criteria. Results showed that ferritin can effectively rule out ID anemia in patients with or without inflammatory disease at cut-offs of 70 and 40 μg/L, respectively. From two studies using ISs calibrated assays that met inclusion criteria, no information emerged on which cut-off should be employed to obtain similar sensitivity. Regarding iron overload, even when the framework was restricted to hereditary hemochromatosis, no synthesis of scientific evidence, if any, about diagnostic accuracy of ferritin was available both before and after ISs introduction. Available evidence of the ferritin diagnostic effectiveness is limited to ID conditions. Recommended cut-offs for this application are, however, based on studies published from 1970 to the 1980s using non-harmonized assays.

Increased Mitochondrial Mass and Mitochondrial DNA Copy Number Are Biomarkers for Benzene Exposure in Hematopoietic Tissue and Leukemia Cells.

Abstract 4426 BackgroundExposure to benzene and its metabolites increases risk of marrow failure disorders, leukemia and other hematological diseases. However, biomarkers of benzene toxicity have not been comprehensively studied in hematopoietic cells and leukemia cells. We previously reported that benzene metabolites may impair electron chain transport and mitochondrial function (3rd WHO Conference on Children's Health and the Environment, 7-10 June 2009). Therefore, we hypothesized that alterations in mitochondrial mass and mitochondrial DNA (mtDNA) may occur in bone marrow cells and leukemia cells after benzene exposure to compensate for damaged mitochondria. Materials and MethodsTotal bone marrow cells from healthy individuals and leukemia cell lines (THP-1, Kasumi-1, K562, Molt-4 and HL-60) were cultured in RPMI media containing 10% fetal bovine serum for 5 days. Benzene was added in cell culture media with 0, 1 and 10mM concentration at 24 hour interval. Cell count was performed using an automated blood cell analyzer (ADVIA120, Siemens, Germany). Viability and apoptosis were assessed by tryptophan blue dye exclusion test and flowcytometry based annexin V staining protocol. Hydrogen peroxide content is measured using the commercial kit (Bioxytech® H2O2-560TM, OXIS International) according to the manufacturer's instructions. Mitochondrial mass, membrane potential and mtDNA copy number were measured using MitoTracker Green, MitoTracker Red probes (Invitrogen), and real time PCR using the QuantiTect SYBR Green PCR kit (Qiagen) and Rotor-Gene 3000 (Corbett Research), respectively. ResultsThe number of cells were gradually increased regardless of concentration of benzene in day 3, and then steadily maintained during 3 weeks culture. Interestingly, the growth of K562 cells showed no growth inhibition effect (three fold increase) after 5-day exposure to benzene. Overall viability of five leukemia cell lines disclosed significant decrease after two week treatment of benzene (about 60% of viability was observed in 3- week suspension culture). The proportion of apoptosis was increased in time and dose dependent manner after 2-week treatment of benzene. Interestingly, mitochondrial contents and membrane potentials were dramatically increased in 3-week suspension culture after benzene exposure at dose dependent manner. The level of hydrogen peroxide significantly elevated after two week treatment of benzene (4.4 ± 1.9 μM/mg protein) compared with non-benzene treatment group (1.2 ± 1.0 μM/mg protein; P = 0.001). The average mtDNA copy number was gradually increased after exposure to benzene. ConclusionsBenzene exposure caused increased mitochondrial mass and mtDNA copy number in response to oxidative stress induced by benzene. So, these mitochondrial changes can be used for biomarkers of benzene toxicity in hematopoietic tissue and leukemia cell. Disclosures:No relevant conflicts of interest to declare.

Influenza surveillance in Serbia: use of rapid cell culture assay

Quantitative measurement of HIV-1 RNA levels in plasma (‘viral load’) plays a central role in clinical management. The choice of assay platform can influence results and treatment decisions.To compare the analytical performance of the new TMA-based Hologic Aptima® HIV-1 Quant Dx assay with that of three PCR-based assays: Abbott RealTime HIV-1, Qiagen Artus® HI Virus-1 QS-RGQ, and Roche CAP/CTM HIV-1 Test v2.Assay performance was evaluated using Acrometrix HIV-1 RNA Standard panels; the 3rd WHO HIV-1 RNA International Standard (12–500 copies/ml; 6 dilutions; 9 replicates); and plasma samples from 191 HIV-positive patients.Aptima showed high (>0.99) precision, accuracy and concordance with the Acrometrix Standards across a wide dynamic range (2.0–6.7 log10 copies/ml). Variance caused up to 2.1 (Aptima), 1.7 (RealTime), 7.5 (Artus), and 1.9 (CAP/CTM) fold changes in the International Standard quantifications at 50–500 copies/ml. HIV-1 RNA detection rates in plasma samples were 141/191 (74%), 119/191 (62%), 108/191 (57%), and 145/191 (76%) for Aptima, RealTime, Artus and CAP/CTM, respectively. For categorising samples either side of 50 copies/ml, Aptima had excellent agreement with RealTime (kappa 0.92; 95% CI 0.87–0.98); lowest agreement was with Artus (kappa 0.79; 95%CI 0.70–0.88). Aptima quantifications were mean 0.12 and 0.06 log10 copies/ml higher compared with RealTime and CAP/CTM, respectively, and 0.05 log10 copies/ml lower compared with Artus. Limits of agreement were narrowest when comparing Aptima to RealTime.The new Aptima HIV assay is sensitive, precise, and accurate. HIV assays exhibit discordance at low HIV-1 RNA copy numbers.