Prevalence of monoclonal gammopathy of undetermined significance in Eswatini: a population-based study in Africa.

BACKGROUND: Although monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma disproportionately affect Black individuals, few epidemiological studies have been conducted on these plasma cell disorders in Africa. Here we describe the prevalence of MGUS in Eswatini and compare our results to the landmark Olmsted County, Minnesota study. METHODS: Between 2016 and 2017, 13 339 residents of Eswatini participated in the Swaziland HIV Incidence Measurement Survey, from which a nationally representative biorepository was created. Plasma samples were then randomly selected and analyzed for MGUS. MGUS prevalence in Eswatini was compared with that of Olmsted County. In addition, demographic and HIV-related associations with MGUS were assessed. RESULTS: Of the 515 samples randomly selected, the median age was 50 years (range = 35-80 years); 60% were female; and 38.6% were HIV positive, of whom 82.4% were on antiretroviral therapy. We found that 68 participants had evidence of MGUS, for a prevalence of 13.2%. HIV status was not significantly associated with MGUS (odds ratio = 1.05, 95% confidence interval = 0.62 to 1.77), but among HIV-positive individuals, MGUS was less frequent for patients on antiretroviral therapy (adjusted odds ratio = 0.31, 95% confidence interval = 0.11 to 0.82). The prevalence of conventional MGUS was similar between Eswatini and Olmsted County (3.4% vs 3.2%-3.4%), whereas the incidence of light-chain MGUS was significantly greater in Eswatini (12.3% vs 0.8%). CONCLUSION: Our study suggests that the incidence of MGUS is similar between ethnicities and raises the question of whether the current definition of light-chain MGUS reliably reflects a true monoclonal protein precursor state. Perhaps the current definition of light-chain MGUS may be capturing alternate etiologies, such as untreated HIV infection.

Field Validation of Limiting-Antigen Avidity Enzyme Immunoassay to Estimate HIV-1 Incidence in Cross-Sectional Survey in Swaziland.

Reliable and accurate laboratory assays to detect recent HIV-1 infection have potential as simple and practical methods of estimating HIV-1 incidence in cross-sectional surveys. This study describes validation of the limiting-antigen (LAg) avidity enzyme immunoassay (EIA) in a cross-sectional national survey, conducted in Swaziland, comparing it to prospective follow-up incidence. As part of the Swaziland HIV-1 Incidence Measurement Survey (SHIMS), 18,172 individuals underwent counseling and HIV rapid testing in a household-based, population survey conducted from December 2010 to June 2011. Plasma samples from HIV-positive persons were classified as recent infections using an incidence testing algorithm with LAg-Avidity EIA (normalized optical density ≤1.5) followed by viral load (VL ≥1,000 copies/mL). All HIV-seronegative samples were tested for acute HIV-1 infection by nucleic acid amplification test (NAAT) pooling. HIV-seronegative individuals who consented to follow-up were retested ∼6 months later to detect observed HIV-1 seroconversion. HIV-1 incidence estimates based on LAg+VL and NAAT were calculated using assay-specific parameters and were compared with prospective incidence estimate. A total of 5,803 (31.9%) of 18,172 survey participants tested HIV seropositive; of these 5,683 (97.9%) were further tested with LAg+VL algorithm. The weighted annualized incidence from the longitudinal cohort study was 2.4% (95% confidence interval 2.0-2.7). Based on cross-sectional testing of HIV positives with LAg+VL algorithm, overall weighted annualized HIV-1 incidence was 2.5% (2.0-3.0), whereas NAAT-based incidence was of 2.6%. In addition, LAg-based incidence in men (1.8%; 1.2-2.5) and women (3.2%; 2.4-3.9) were similar to estimates based on observed incidence (men = 1.7%, women = 3.1%). Changes in HIV-1 incidence with age in men and women further validate plausibility of the algorithm. These results demonstrate that the LAg EIA, in a serial algorithm with VL, is a cost-effective tool to estimate HIV-1 incidence in cross-sectional surveys.

Poor performance of the determine HIV-1/2 Ag/Ab combo fourth-generation rapid test for detection of acute infections in a National Household Survey in Swaziland.

Fourth-generation HIV rapid tests (RTs) claim to detect both p24 antigen (Ag) and HIV antibodies (Ab) for early identification of acute infections, important for targeting prevention and reducing HIV transmission. In a nationally representative household survey in Swaziland, 18,172 adults, age 18 to 49 years, received home-based HIV rapid testing in 2010 and 2011. Of the 18,172 individuals, 5,822 (32.0%) were Ab positive (Ab(+)) by the Determine HIV-1/2 Ab/Ab combo test, and 5,789 (99.4%) of those were confirmed to be reactive in the Uni-Gold test. Determine combo identified 12 individuals as having acute infections (Ag(+)/Ab negative [Ab(-)]); however, none had detectable HIV-1 RNA and 8 of 12 remained HIV negative at their 6-week follow-up visit (4 were lost to follow-up). All RT-nonreactive samples were pooled and tested by nucleic acid amplification testing (NAAT) to identify acute infections. NAAT identified 13 (0.1%) of the 12,338 HIV antibody-negative specimens as HIV RNA positive, with RNA levels ranging from 300 to >10,000,000 copies/ml. However, none of them were Ag(+) by Determine combo. Follow-up testing of 12 of the 13 NAAT-positive individuals at 6 months demonstrated 12 seroconversions (1 individual was lost to follow-up). Therefore, the Determine combo test had a sensitivity of 0% (95% confidence interval, 0 to 28) and positive predictive value of 0% for the detection of acute infections. The ability of the 4th-generation Determine combo to detect antigen was very poor in Swaziland. Thus, the Determine combo test does not add any value to the current testing algorithm; rather, it adds additional costs and complexity to HIV diagnosis. The detection of acute HIV infections may need to rely on other testing strategies.