Estimation of Plasmodium falciparum Transmission Intensity in Lilongwe, Malawi, by Microscopy, Rapid Diagnostic Testing, and Nucleic Acid Detection

Estimates of malaria transmission intensity (MTI) typically rely upon microscopy or rapid diagnostic testing (RDT). However, these methods are less sensitive than nucleic acid amplification techniques and may underestimate parasite prevalence. We compared microscopy, RDT, and polymerase chain reaction (PCR) for the diagnosis of Plasmodium falciparum parasitemia as part of an MTI study of 800 children and adults conducted in Lilongwe, Malawi. PCR detected more cases of parasitemia than microscopy or RDT. Age less than 5 years predicted parasitemia detected by PCR alone (adjusted odds ratio = 1.61, 95% confidence interval = 1.09–2.38, Wald P = 0.02). In addition, we identified one P. falciparum parasite with a false-negative RDT result due to a suspected deletion of the histidine-rich protein 2 (hrp2) gene and used a novel, ultrasensitive PCR assay to detect low-level parasitemia missed by traditional PCR. Molecular methods should be considered for use in future transmission studies as a supplement to RDT or microscopy

Measures of viral load using Abbott RealTime HIV-1 Assay on venous and fingerstick dried blood spots from provider-collected specimens in Malawian District Hospitals

Viral suppression is a key indicator of antiretroviral therapy (ART) response among HIV-infected patients. Dried blood spots (DBS) are an appealing alternative to conventional plasma-based virologic testing, improving access to monitoring in resource-limited settings. However, validity of DBS obtained from fingerstick in field settings remains unknown

Performance of Xpert® MTB/RIF among tuberculosis outpatients in Lilongwe, Malawi

Background: Xpert® MTB/RIF is a molecular test for the detection of Mycobacterium tuberculosis and rifampicin resistance. It is considered to be a great advance over smear microscopy and culture. However, there is very little information regarding the performance characteristics of Xpert MTB/RIF in Malawi. Objective: We aimed to evaluate the performance of Xpert MTB/RIF in a Malawian setting. Methods: Stored sputum pellets were processed on Xpert MTB/RIF between June 2012 andMay 2014. Results were compared to mycobacteria growth indicator tube and Löwenstein-Jensen cultures, LED fluorescent microscopy and GenoType® MTBDRplus assay. Rifampicinresistance was confirmed by DNA sequencing. Results: Of the 348 specimens with valid Xpert MTB/RIF results, 129/348 (37%) were smearpositive and 198/348 (57%) were culture-positive. Xpert MTB/RIF demonstrated a sensitivity of 93.8% (95% CI 89.4% – 96.8%) and specificity of 97.4% (95% CI 93.5% – 99.3%), with a positive predictive value of 97.8% (95% CI 94.6% – 99.4%) and a negative predictive value of 92.6% (95% CI 87.4% – 96.1%). Xpert MTB/RIF correctly identified 185/186 (99.5%) rifampicin sensitive and 2/2 (100%) rifampicin-resistant M. tuberculosis strains. Mutations were notdetected by sequencing in one isolate which was rifampicin resistant on Xpert MTB/RIF butsensitive on MTBDRplus. Four non-tuberculous mycobacteria grew from four smear-negativespecimens, namely, M. avium (n = 1) and M. intracellulare (n = 3). No cross-reactivity wasobserved with any of the non-tuberculous mycobacteria when using Xpert MTB/RIF. Conclusion: When fully implemented, Xpert MTB/RIF may have an impact on patient care inMalawi. The increased diagnostic yield of Xpert MTB/RIF over smear microscopy can increaselaboratory-confirmed tuberculosis detection and ensure that treatment is given to appropriateindividuals or groups

Molecular characterisation of rifampicin-resistant <i>Mycobacterium tuberculosis</i> strains from Malawi

Background: Availability and access to the detection of resistance to anti-tuberculosis drug sremains a significant challenge in Malawi due to limited diagnostic services. The Xpert® MTB/RIF can detect Mycobacterium tuberculosis and resistance to rifampicin in a single, rapid assay. Rifampicin-resistant M. tuberculosis has not been well studied in Malawi. Objectives: We aimed to determine mutations in the rifampicin resistance determining region (RRDR) of the rpoB gene of M. tuberculosis strains which were defined as resistant to rifampicin by the Xpert MTB/RIF assay. Methods: Rifampicin-resistant isolates from 43 adult patients (≥ 18 years) from various districts of Malawi were characterised for mutations in the RRDR (codons 507–533) of the rpoB gene by DNA sequencing. Results: Mutations were found in 37/43 (86%) of the resistant isolates in codons 511, 512, 513,516, 522, 526 and 531. The most common mutations were in codons 526 (38%), 531 (29.7%) and 516 (16.2%). Mutations were not found in 6/43 (14%) of the resistant isolates. No novel rpoB mutations other than those previously described were found among the rifampicin-resistant M. tuberculosis complex strains. Conclusion: This study is the first to characterise rifampicin resistance in Malawi. The chaintermination DNA sequencing employed in this study is a standard method for the determination of nucleotide sequences and can be used to confirm rifampicin resistance obtained using other assays, including the Xpert MTB/RIF. Further molecular cluster analysis, such as spoligotyping and DNA finger printing, is still required to determine transmission dynamics and the epidemiological link of the mutated strains

Blood and genital fluid viral load trajectories among treated and untreated persons with acute HIV infection in Malawi

Background: Persons with acute HIV infection (AHI) are highly infectious and responsible for a disproportionate share of incident infections. Immediate antiretroviral therapy (ART) rapidly reduces blood viral loads (VLs), but genital VLs after ART initiation during AHI are less well described. Setting: Lilongwe, Malawi, 2012-2014. Methods: HIV-seronegative and HIV-serodiscordant persons aged ≥18 years were screened for AHI (RNA positive) and randomized to standard of care, behavioral intervention, or behavioral intervention plus short-term ART (raltegravir/emtricitabine/tenofovir) (1:2:2). Persons who were ART eligible under Malawi guidelines could receive first-line therapy. Blood and genital VLs were assessed at weeks 1, 4, 8, and 12. Fisher's Exact test was used to compare viral suppression by ART status. Results: Overall, 46 persons with AHI were enrolled; of whom, 17 started ART within 12 weeks. Median blood VL at AHI diagnosis was 836,115 copies/mL. At week 12, 7% (1/14) of those who initiated ART had a blood VL of ≥400 copies/mL, compared with 100% (23/23; P < 0.0001) of those who did not initiate ART (median VL: 61,605 copies/mL). Median genital VL at week 1 was 772 copies/mL, with 13 of 22 (59%) having VL of ≥400 copies/mL. At week 12, 0 of 10 (0%) of those who initiated ART had genital VL of ≥400 copies/mL, compared with 7 of 15 (47%) of those who did not initiate ART (P = 0.02). Conclusion: Although highly correlated, VLs in blood and genital fluids occupy discrete biological compartments with distinct virologic dynamics. Our results corroborate the dramatic reduction in both compartments after ART initiation. Increasing AHI screening and rapidly initiating treatment is key to interrupting transmission

Measures of viral load using Abbott RealTime HIV-1 Assay on venous and fingerstick dried blood spots from provider-collected specimens in Malawian District Hospitals

BACKGROUND: Viral suppression is a key indicator of antiretroviral therapy (ART) response among HIV-infected patients. Dried blood spots (DBS) are an appealing alternative to conventional plasma-based virologic testing, improving access to monitoring in resource-limited settings. However, validity of DBS obtained from fingerstick in field settings remains unknown. OBJECTIVES: Investigate feasibility and accuracy of DBS vs plasma collected by healthcare workers in real-world settings of remote hospitals in Malawi. Compare venous DBS to fingerstick DBS for identifying treatment failure. STUDY DESIGN: We recruited patients from ART clinics at two district hospitals in Malawi, collecting plasma, venous DBS (vDBS), and fingerstick DBS (fsDBS) cards for the first 149 patients, and vDBS and fsDBS only for the subsequent 398 patients. Specimens were tested using Abbott RealTime HIV-1 Assay (lower detection limit 40 copies/ml (plasma) and 550 copies/ml (DBS)). RESULTS: 21/149 (14.1%) had detectable viremia (>1.6 log copies/ml), 13 of which were detectable for plasma, vDBS, and fsDBS. Linear regression demonstrated high correlation for plasma vs. DBS (vDBS: β=1.19, R(2) 0.93 (p<0.0001); fsDBS β=1.20, R(2) 0.90 (p<0.0001)) and vDBS vs. fsDBS (β=0.88, R(2) 0.73, (p<0.0001)). Mean difference between plasma and vDBS was 0.51 log copies/ml [SD: 0.33] and plasma and fsDBS 0.46 log copies/ml [SD: 0.30]. At 5000 copies/ml, sensitivity was 100%, and specificity was 98.6% and 97.8% for vDBS and fsDBS, respectively, compared to plasma. CONCLUSIONS: DBS from venipuncture and fingerstick perform well at the failure threshold of 5000 copies/ml. Fingerstick specimen source may improve access to virologic treatment monitoring in resource-limited settings given task-shifting in high-volume, low-resource facilities