Combatting Global Infectious Diseases: A Network Effect of Specimen Referral Systems.

The recent Ebola virus outbreak in West Africa clearly demonstrated the critical role of laboratory systems and networks in responding to epidemics. Because of the huge challenges in establishing functional laboratories at all tiers of health systems in developing countries, strengthening specimen referral networks is critical. In this review article, we propose a platform strategy for developing specimen referral networks based on 2 models: centralized and decentralized laboratory specimen referral networks. These models have been shown to be effective in patient management in programs in resource-limited settings. Both models lead to reduced turnaround time and retain flexibility for integrating different specimen types. In Haiti, decentralized specimen referral systems resulted in a 182% increase in patients enrolling in human immunodeficiency virus treatment programs within 6 months. In Uganda, cost savings of up to 62% were observed with a centralized model. A platform strategy will create a network effect that will benefit multiple disease programs.

Trends in Prevalence of Advanced HIV Disease at Antiretroviral Therapy Enrollment - 10 Countries, 2004-2015.

Monitoring prevalence of advanced human immunodeficiency virus (HIV) disease (i.e., CD4+ T-cell count <200 cells/µL) among persons starting antiretroviral therapy (ART) is important to understand ART program outcomes, inform HIV prevention strategy, and forecast need for adjunctive therapies.*,†,§ To assess trends in prevalence of advanced disease at ART initiation in 10 high-burden countries during 2004-2015, records of 694,138 ART enrollees aged ≥15 years from 797 ART facilities were analyzed. Availability of national electronic medical record systems allowed up-to-date evaluation of trends in Haiti (2004-2015), Mozambique (2004-2014), and Namibia (2004-2012), where prevalence of advanced disease at ART initiation declined from 75% to 34% (p<0.001), 73% to 37% (p<0.001), and 80% to 41% (p<0.001), respectively. Significant declines in prevalence of advanced disease during 2004-2011 were observed in Nigeria, Swaziland, Uganda, Vietnam, and Zimbabwe. The encouraging declines in prevalence of advanced disease at ART enrollment are likely due to scale-up of testing and treatment services and ART-eligibility guidelines encouraging earlier ART initiation. However, in 2015, approximately a third of new ART patients still initiated ART with advanced HIV disease. To reduce prevalence of advanced disease at ART initiation, adoption of World Health Organization (WHO)-recommended "treat-all" guidelines and strategies to facilitate earlier HIV testing and treatment are needed to reduce HIV-related mortality and HIV incidence.

Antiretroviral therapy enrollment characteristics and outcomes among HIV-infected adolescents and young adults compared with older adults--seven African countries, 2004-2013.

Although scale-up of antiretroviral therapy (ART) since 2005 has contributed to declines of about 30% in the global annual number of human immunodeficiency (HIV)-related deaths and declines in global HIV incidence, estimated annual HIV-related deaths among adolescents have increased by about 50% and estimated adolescent HIV incidence has been relatively stable. In 2012, an estimated 2,500 (40%) of all 6,300 daily new HIV infections occurred among persons aged 15-24 years. Difficulty enrolling adolescents and young adults in ART and high rates of loss to follow-up (LTFU) after ART initiation might be contributing to mortality and HIV incidence in this age group, but data are limited. To evaluate age-related ART retention challenges, data from retrospective cohort studies conducted in seven African countries among 16,421 patients, aged ≥15 years at enrollment, who initiated ART during 2004-2012 were analyzed. ART enrollment and outcome data were compared among three groups defined by age at enrollment: adolescents and young adults (aged 15-24 years), middle-aged adults (aged 25-49 years), and older adults (aged ≥50 years). Enrollees aged 15-24 years were predominantly female (81%-92%), commonly pregnant (3%-32% of females), unmarried (54%-73%), and, in four countries with employment data, unemployed (53%-86%). In comparison, older adults were more likely to be male (p<0.001), employed (p<0.001), and married, (p<0.05 in five countries). Compared with older adults, adolescents and young adults had higher LTFU rates in all seven countries, reaching statistical significance in three countries in crude and multivariable analyses. Evidence-based interventions to reduce LTFU for adolescent and young adult ART enrollees could help reduce mortality and HIV incidence in this age group.

Development, Assessment, and Outcomes of a Community-Based Model of Antiretroviral Care in Western Kenya Through a Cluster-Randomized Control Trial.

OBJECTIVE: To develop and assess an alternative care model using community-based groups for people living with HIV and facilitate by lay personnel. METHODS: Geographic locations in the Academic Model Providing Access to Healthcare Kitale clinic catchment were randomized to standard of care versus a community-based care group (ART Co-op). Adults stable on antiretroviral therapy and virally suppressed were eligible. Research Assistant-led ART Co-ops met in the community every 3 months. Participants were seen in the HIV clinic only if referred. CD4 count and viral load were measured in clinic at enrollment and after 12 months. Retention, viral suppression, and clinic utilization were compared between groups using χ2, Fisher exact, and Wilcoxon rank sum tests. RESULTS: At 12 months, there were no significant differences in mean CD4 count or viral load suppression. There was a significant difference in patient retention in assigned study group between the intervention and control group (81.6% vs 98.6%; P < 0.001), with a number of intervention patients withdrawing because of stigma, relocation, pregnancy, and work conflicts. All participants, however, were retained in an HIV care program for the study duration. The median number of clinic visits was lower for the intervention group than that for the control group (0 vs 3; P < 0.001). CONCLUSIONS: Individuals retained in a community-based HIV care model had clinical outcomes equivalent to those receiving clinic-based care. This innovative model of HIV care addresses the problems of insufficient health care personnel and patient retention barriers, including time, distance, and cost to attend clinic, and has the potential for wider implementation.

The emergence of HIV/AIDS in the Americas and beyond.

HIV-1 group M subtype B was the first HIV discovered and is the predominant variant of AIDS virus in most countries outside of sub-Saharan Africa. However, the circumstances of its origin and emergence remain unresolved. Here we propose a geographic sequence and time line for the origin of subtype B and the emergence of pandemic HIV/AIDS out of Africa. Using HIV-1 gene sequences recovered from archival samples from some of the earliest known Haitian AIDS patients, we find that subtype B likely moved from Africa to Haiti in or around 1966 (1962-1970) and then spread there for some years before successfully dispersing elsewhere. A "pandemic" clade, encompassing the vast majority of non-Haitian subtype B infections in the United States and elsewhere around the world, subsequently emerged after a single migration of the virus out of Haiti in or around 1969 (1966-1972). Haiti appears to have the oldest HIV/AIDS epidemic outside sub-Saharan Africa and the most genetically diverse subtype B epidemic, which might present challenges for HIV-1 vaccine design and testing. The emergence of the pandemic variant of subtype B was an important turning point in the history of AIDS, but its spread was likely driven by ecological rather than evolutionary factors. Our results suggest that HIV-1 circulated cryptically in the United States for approximately 12 years before the recognition of AIDS in 1981.

Human herpesvirus 8 presence and viral load are associated with the progression of AIDS-associated Kaposi's sarcoma.

OBJECTIVE: We present the largest longitudinal study to date that examines the association between Kaposi's Sarcoma (KS) disease progression and the presence and viral load of human herpesvirus 8 (HHV-8). METHODS: Ninety-six men were enrolled at HIV clinics in Atlanta, Georgia, who had KS (n = 47) or were without KS but seropositive for HHV-8. Visits occurred at 6-month intervals for 2 years at which the patient's KS status was evaluated and oral fluid and blood were collected for quantification of HHV-8 DNA and antibodies. RESULTS: The presence of HHV-8 DNA in blood was more common (P < 0.001) and the viral load higher (P < 0.001) in men with KS in comparison with men without KS. Mean HHV-8 viral loads in blood and oral fluids were associated with disease status, being highest among patients with progressing KS, intermediate among patients with stable KS, and lowest among patients with regressing KS. Consistent with our previous report high antibody titers to HHV-8 orf 65 were inversely associated with HHV-8 shedding in oral fluid. CONCLUSIONS: We observed a significant association between changes in KS disease severity and the presence and viral load of HHV-8. HHV-8 viral load in blood may provide useful information to clinicians for assessment of the risk of further disease progression in patients with KS.

Clinical and virological characterization of persistent human infection with simian foamy viruses.

Persons occupationally exposed to nonhuman primates (NHPs) can be persistently infected with simian foamy virus (SFV). The clinical significance and person-to-person transmissibility of zoonotic SFV infection is unclear. Seven SFV-infected men responded to annual structured interviews and provided whole blood, oral, and urogenital specimens for study. Wives were tested for SFV infection. Proviral DNA was consistently detected by PCR in PBMCs of infected men and inconsistently in oral or urogenital samples. SFV was infrequently cultured from their PBMCs and throat swabs. Despite this and a long period of intimate exposure (median 20 years), wives were SFV negative. Most participants reported nonspecific symptoms and diseases common to aging. However, one of two persons with mild thrombocytopenia had clinically asymptomatic nonprogressive, monoclonal natural killer cell lymphocytosis of unclear relationship to SFV. All participants worked with NHPs before 1988 using mucocutaneous protection inconsistently; 57% described percutaneous injuries involving the infecting NHP species. SFV likely transmits to humans through both percutaneous and mucocutaneous exposures to NHP body fluids. Limited follow-up has not identified SFV-associated illness and secondary transmission among humans.

Association of CCR5 human haplogroup E with rapid HIV type 1 disease progression.

The combination of unique single nucleotide polymorphisms in the CCR5 regulatory and in the CCR2 and CCR5 coding regions, defined nine CCR5 human haplogroups (HH): HHA-HHE, HHF*1, HHF*2, HHG*1, and HHG*2. Here we examined the distribution of CCR5 HH and their association with HIV infection and disease progression in 36 HIV-seronegative and 76 HIV-seropositive whites from North America and Spain [28 rapid progressors (RP) and 48 slow progressors (SP)]. Although analyses revealed that HHE frequencies were similar between HIV-seronegative and HIV-seropositive groups (25.0% vs. 32.2%, p > 0.05), HHE frequency in RP was significantly higher than that in SP (48.2% vs. 22.9%, p = 0.002). Survival analysis also showed that HHE heterozygous and homozygous were associated with an accelerated CD4 cell count decline to less than 200 cells/microL (adjusted RH 2.44, p = 0.045; adjusted RH = 3.12, p = 0.037, respectively). These data provide further evidence that CCR5 human haplogroups influence HIV-1 disease progression in HIV-infected persons.

Applying public health strategies to primary immunodeficiency diseases: a potential approach to genetic disorders.

Primary immunodeficiency (PI) diseases are a group of primarily single-gene disorders of the immune system. Approximately 100 separate PI diseases have been described, but <20 probably account for >90% of cases. Although diverse, PI diseases share the common feature of susceptibility to infection and result in substantial morbidity and shortened life spans. Most important, prompt diagnosis and treatment can now lead to life-saving treatment and result in marked improvements in the quality and length of life for persons with PI diseases. In November 2001, a workshop was convened by CDC in Atlanta, Georgia, to discuss ways to improve health outcomes among persons with PI disease. A multidisciplinary panel of persons knowledgeable in PI diseases and public health met to identify and discuss public health strategies that can be applied to PI diseases and possibly for other genetic disorders. A systematic assessment based on the established public health framework was applied to the growing group of PI diseases, whose diverse genetic mutations span multiple components of the immune system but all lead to increased incidence and severity of infections. During the meeting, specialists in clinical immunology, public health, genetics, pediatrics, health communication, and ethics from state and federal agencies, academic centers, professional organizations, and advocacy foundations discussed the four components of the public health framework as they relate to PI diseases. These four components include 1) public health assessment (application of traditional public health methods to assess the occurrence and impact of PI diseases on communities); 2) population-based interventions (development, implementation, and evaluation of screening tests administered to newborns and clinical algorithms for early recognition of symptomatic persons to facilitate the earliest possible diagnosis and treatment for PI diseases); 3) evaluation of screening and diagnostic tools (to ensure their quality and appropriateness for identification of patients with PI diseases); and 4) communication (communication with and information dissemination to health-care providers and the public to facilitate prompt and appropriate diagnosis and intervention). The working group's deliberations focused on challenges and opportunities, priority research questions, and recommendations for future action for these four components. These recommendations, developed by workshop participants, will be useful to medical and public health professionals who are evaluating methods to increase recognition of PI diseases and other genetic disorders.

Temporal Trends in Patient Characteristics and Outcomes Among Children Enrolled in Mozambique's National Antiretroviral Therapy Program.

BACKGROUND: During 2004-2009, >12,000 children (<15 years old) initiated antiretroviral therapy (ART) in Mozambique. Nationally representative outcomes and temporal trends in outcomes were investigated. METHODS: Rates of death, loss to follow-up (LTFU) and attrition (death or LTFU) were evaluated in a nationally representative sample of 1054 children, who initiated ART during 2004-2009 at 25 facilities randomly selected using probability-proportional-to-size sampling. RESULTS: At ART initiation during 2004-2009, 50% were male; median age was 3.3 years; median CD4% was 13%; median CD4 count was 375 cells/µL; median weight-for-age Z score was -2.1. During 2004-2009, median time from HIV diagnosis to care initiation declined from 33 to 0 days (P = 0.001); median time from care to ART declined from 93 to 62 days (P = 0.004); the percentage aged <2 at ART initiation increased from 16% to 48% (P = 0.021); the percentage of patients with prior tuberculosis declined from 50% to 10% (P = 0.009); and the percentage with prior lymphocytic interstitial pneumonia declined from 16% to 1% (P < 0.001). Over 2652 person-years of ART, 183 children became LTFU and 26 died. Twelve-month attrition was 11% overall but increased from 3% to 22% during 2004-2009, mainly because of increases in 12-month LTFU (from 3% to 18%). CONCLUSION: Declines in the prevalence of markers of advanced HIV disease at ART initiation probably reflect increasing ART access. However, 12-month LTFU increased during program expansion, and this negated any program improvements in outcomes that might have resulted from earlier ART initiation.

CD4 enumeration technologies: a systematic review of test performance for determining eligibility for antiretroviral therapy.

BACKGROUND: Measurement of CD4+ T-lymphocytes (CD4) is a crucial parameter in the management of HIV patients, particularly in determining eligibility to initiate antiretroviral treatment (ART). A number of technologies exist for CD4 enumeration, with considerable variation in cost, complexity, and operational requirements. We conducted a systematic review of the performance of technologies for CD4 enumeration. METHODS AND FINDINGS: Studies were identified by searching electronic databases MEDLINE and EMBASE using a pre-defined search strategy. Data on test accuracy and precision included bias and limits of agreement with a reference standard, and misclassification probabilities around CD4 thresholds of 200 and 350 cells/µl over a clinically relevant range. The secondary outcome measure was test imprecision, expressed as % coefficient of variation. Thirty-two studies evaluating 15 CD4 technologies were included, of which less than half presented data on bias and misclassification compared to the same reference technology. At CD4 counts <350 cells/µl, bias ranged from -35.2 to +13.1 cells/µl while at counts >350 cells/µl, bias ranged from -70.7 to +47 cells/µl, compared to the BD FACSCount as a reference technology. Misclassification around the threshold of 350 cells/µl ranged from 1-29% for upward classification, resulting in under-treatment, and 7-68% for downward classification resulting in overtreatment. Less than half of these studies reported within laboratory precision or reproducibility of the CD4 values obtained. CONCLUSIONS: A wide range of bias and percent misclassification around treatment thresholds were reported on the CD4 enumeration technologies included in this review, with few studies reporting assay precision. The lack of standardised methodology on test evaluation, including the use of different reference standards, is a barrier to assessing relative assay performance and could hinder the introduction of new point-of-care assays in countries where they are most needed.

Repeated measures study of human herpesvirus 8 (HHV-8) DNA and antibodies in men seropositive for both HHV-8 and HIV.

OBJECTIVE: To study the natural history and pathogenesis of human herpesvirus 8 (HHV-8) infection in HHV-8-seropositive, immunosuppressed men. DESIGN: Longitudinal study of 87 HHV-8- and HIV-seropositive men [42 with Kaposi's sarcoma (KS)] during four visits over a 2 month period. METHODS: : Patients provided oral fluid and blood. HHV-8 antibody titers were measured with peptide-based enzyme-linked immunosorbent assays (ELISA) for ORF65 and K8.1; HHV-8 DNA was detected with polymerase chain reaction ELISA. RESULTS: HHV-8 DNA was present in oral fluid or peripheral blood mononuclear cells (PBMC) at one or more of the four visits in 71% of men with KS and 56% of men without KS. The strongest correlate of HHV-8 DNA in PBMC was the presence of KS [odds ratio (OR), 8.7; 95% confidence interval (CI), 3.4-22]. Detection of HHV-8 DNA in oral fluid or PBMC was often intermittent, but individuals who shed virus at one time point were more likely to shed at other times. Some men had incomplete epitope recognition in their anti-HHV-8 antibody response. High antibody titers were associated with the absence of circulating HHV-8, particularly for the ORF65 seroassay (OR, 0.16; 95% CI, 0.05-0.51). CONCLUSIONS: Among HHV-8 seropositive men, circulating virus is common even in the absence of disease. The link between KS and HHV-8 DNA in PBMC suggests that anti-herpes drugs may impede KS development or progression. Seroassays should target multiple epitopes to achieve maximal sensitivity. HHV-8 replication may be limited by high antibody titers or other immune function for which antibodies are a marker.

Temporal relationship between V1V2 variation, macrophage replication, and coreceptor adaptation during HIV-1 disease progression.

BACKGROUND: Specific mutations in VPR and V2 potentially restrict HIV-1 replication in macrophages. Such restriction could potentially limit HIV replication in long-term non-progressors (LTNP), thus accounting for low viral load and delayed progression to AIDS. OBJECTIVE: To examine whether a specific VPR phenotype (truncated versus non-truncated) correlates with disease progression and whether elongated V2 restricts viral replication in macrophages or alters viral tropism. METHODS: Sequence analysis was carried for VPR and V1-V3 env from four rapid progressors (RPs), six late progressors (LPs), and three LTNPs in cohort of HIV-1-infected homosexual men. The replication kinetics of sequential isolates was examined in primary CD4 cells and macrophages and coreceptor usage was determined by GHOST infection assays. RESULTS: No differences were found in the VPR protein from RP and LTNP isolates. Analysis of the V2 region revealed that all RPs maintained similar V2 lengths (40 aa), whereas LPs and LTNPs acquired additional amino acids (2-13 aa) in the V2 region. Coreceptor specificity revealed that RP switch from CCR5 to multiple coreceptor usage, whereas LTNPs maintained R5 viruses. Sequential isolates from each group revealed comparable replication efficiencies in both T-cells and macrophages, regardless of the V2 length or coreceptor utilization. In addition, cross-section analysis of six LTNPs from Australia revealed extended V2 with consistent usage of CCR5 coreceptor. CONCLUSION: The present results suggest that acquisition of a V2 extension over time in HIV-1-infected LPs/LTNPs appears to correlate with maintenance of CCR5 usage among LTNPs. These findings may be important for a better understanding of the host interactions and disease progression.

Risk factors for Kaposi's sarcoma in men seropositive for both human herpesvirus 8 and human immunodeficiency virus.

OBJECTIVE: To identify risk factors for Kaposi's sarcoma (KS) among men seropositive for both human herpesvirus 8 (HHV-8) and HIV. DESIGN: Cross-sectional study of 91 HHV-8 seropositive, HIV seropositive men who have sex with men (57 with KS), and 70 controls at lower risk for KS. METHODS: Patients received clinical evaluations. Blood, oral fluids, semen, rectal brush, rectal swab, and urine were collected, and tests for HHV-8 were performed. RESULTS: Men with KS were more likely to have HHV-8 DNA in peripheral blood mononuclear cells (PBMC) than men without KS [35.1 versus 5.9%, odds ratio (OR), 8.6, 95% confidence interval (CI), 1.9-39.9]. The prevalence of HHV-8 DNA in oral fluids was similar for the two groups (37.0 versus 32.4%; OR, 1.2; 95% CI, 0.5-3.0). HHV-8 DNA was rarely detected in specimens of other types from these men, or in any specimens from the 70 controls. Among men with KS, HHV-8 DNA in PBMC was associated with new KS lesions (OR, 4.5; 95% CI, 1.4-14.5), and HHV-8 DNA in oral fluids was associated with oropharyngeal KS lesions (OR, 3.1; 95% CI, 1.0-10.1). Men with high HHV-8 antibody titers were more likely to have KS (OR, 9.6; 95% CI, 1.2-78.2), but were less likely to have new KS lesions (OR, 0.2; 95% CI, 0.0-1.1) or HHV-8 DNA in PBMC (OR, 0.2; 95% CI, 0.0-1.6) or oral fluids (OR, undefined; = 0.001). CONCLUSIONS: In HHV-8- and HIV-seropositive men, HHV-8 DNA is associated with KS. Among men without KS, HHV-8 DNA is most commonly found in oral fluids. High HHV-8 antibody titers may protect against circulating HHV-8 and new KS lesions.

Development and characterization of a bead-based, multiplex assay for estimation of recent HIV type 1 infection.

Estimation of HIV-1 incidence is an important public health tool for understanding the status of the epidemic, identifying high-risk populations, and assessing various intervention strategies. Several laboratory-based methods have been developed for distinguishing recent from long-term HIV-1 infection; however, each exhibits some degree of misclassification, particularly among AIDS patients and those taking antiretroviral therapy (ART). To improve upon the limitations associated with measuring responses to a single analyte, we have developed a bead-based, multiplex assay for determination of HIV recent infection based on total antibody binding and antibody avidity to multiple analytes. An HIV-specific, multiplex panel was created by coupling the recombinant HIV-1 proteins p66, gp120, gp160, and gp41 to Bio-Plex COOH microspheres. Longitudinal plasma specimens from recent seroconverters were tested for reactivity to the coupled microspheres using the Bio-Plex 200 System. For each analyte, HIV-specific antibody binding and avidity increased for 1-2 years post-seroconversion, leading to a significant difference in reactivity between recent and long-term specimens. While the potential for misclassification of individuals diagnosed with AIDS or receiving ART appears to be minimal with avidity measures, the impact on total antibody binding was variable, depending on the individual analyte. This bead-based, HIV-specific multiplex assay measures several distinct immune responses in a single assay plate, allowing for sampling of multiple analytes in the determination of recent infection, which could aid in the development of improved statistical methods or algorithms that will more accurately estimate HIV incidence.

A quality management systems approach for CD4 testing in resource-poor settings.

Quality assurance (QA) is a systematic process to monitor and improve clinical laboratory practices. The fundamental components of a laboratory QA program include providing a functional and safe laboratory environment, trained and competent personnel, maintained equipment, adequate supplies and reagents, testing of appropriate specimens, internal monitoring of quality, accurate reporting, and external quality assessments. These components are necessary to provide accurate and precise CD4 T-cell counts, an essential test to evaluate start of and monitor effectiveness of antiretroviral therapy for HIV-infected patients. In recent years, CD4 testing has expanded dramatically in resource-limited settings. Information on a CD4 QA program as described in this article will provide guidelines not only for clinical laboratory staff but also for managers of programs responsible for supporting CD4 testing. All agencies involved in implementing CD4 testing must understand the needs of the laboratory and provide advocacy, guidance, and financial support to established CD4 testing sites and programs. This article describes and explains the procedures that must be put in place to provide reliable CD4 determinations in a variety of settings.

The WHO/PEPFAR collaboration to prepare an operations manual for HIV prevention, care, and treatment at primary health centers in high-prevalence, resource-constrained settings: defining laboratory services.

The expansion of HIV/AIDS care and treatment in resource-constrained countries, especially in sub-Saharan Africa, has generally developed in a top-down manner. Further expansion will involve primary health centers where human and other resources are limited. This article describes the World Health Organization/President's Emergency Plan for AIDS Relief collaboration formed to help scale up HIV services in primary health centers in high-prevalence, resource-constrained settings. It reviews the contents of the Operations Manual developed, with emphasis on the Laboratory Services chapter, which discusses essential laboratory services, both at the center and the district hospital level, laboratory safety, laboratory testing, specimen transport, how to set up a laboratory, human resources, equipment maintenance, training materials, and references. The chapter provides specific information on essential tests and generic job aids for them. It also includes annexes containing a list of laboratory supplies for the health center and sample forms.

A North American multilaboratory study of CD4 counts using flow cytometric panLeukogating (PLG): a NIAID-DAIDS Immunology Quality Assessment Program Study.

BACKGROUND: The global HIV/AIDS pandemic and guidelines for initiating anti-retroviral therapy (ART) and opportunistic infection prophylaxis demand affordable, reliable, and accurate CD4 testing. A simple innovative approach applicable to existing technology that has been successfully applied in resource-challenged settings, PanLeukogated CD4 (PLG), could offer solutions for cost saving and improved precision. METHODS: Day-old whole blood from 99 HIV+ donors was simultaneously studied in five North-American laboratories to compare the performance of their predicate methods with the dual-platform PLG method. The predicate technology included varying 4-color CD45/CD3/CD4/CD8 protocols on different flow cytometers. Each laboratory also assayed eight replicate specimens of day-old blood from 10 to 14 local donors. Bias and precision of predicate and PLG methods was studied between- and within-participating laboratories. RESULTS: Significantly (P < 0.0001) improved between-laboratory precision/coefficient of variation (CV%) was noted using the PLG method (overall median 9.3% vs. predicate median CV 13.1%). Within-laboratory precision was also significantly (P < 0.0001) better overall using PLG (median 4.6% vs. predicate median CV 6.2%) and in 3 of the 5 laboratories. PLG counts tended to be 11% smaller than predicate methods (P < 0.0001) for shipped (median of predicate-PLG = 31) and local specimens (median of predicate-PLG = 23), both overall and in 4 of 5 laboratories (median decreases of 4, 16, 20, and 21% in shipped specimens); the other laboratory had a median increase of 5%. CONCLUSION: Laboratories using predicate CD4 methods similar to those in this study could improve their between-laboratory and their within-laboratory precision, and reduce costs, by switching to the PLG method after adequate training, if a change (usually, a decrease) in CD4 counts is acceptable to their health systems.