Fig 1.
Overview of employed diagnostic procedures.
(A) Diagnostic scheme. Procedures included history of eyeworm (B) assessed by the RAPLOA questionnaire, an in-house Loa loa IgG ELISA using crude adult worm antigen (C), a rapid diagnostic test detecting antibodies against the Ll-SXP-1 antigen (D), direct microfilaria detection including microscopy of Giemsa-stained thick blood smears (E) and saponin lysis (F), as well as a L. loa qPCR (G).
Table 1.
The PCR settings for the Loa loa qPCR and Mansonella real-time FRET assay.
Table 2.
Sensitivity, specificity, positive and negative predictive values of the Loa loa qPCR, in-house ELISA and Ll-SXP-1-RDT to detect loiasis defined by either a positive life-time history of eyeworm assessed by the RAPLOA questionnaire and/or detectable microfilaremia.
Fig 2.
Results of exploratory test analysis of microfilaremic loiasis.
Linear regression models showing the association between A) Ct values of the qPCR, B) arbitrary antibody units (AU) of the IgG ELISA and C) reader units (RU) of the Ll-SXP-1-RDT, and L. loa microfilarial density assessed by microscopy. Percentages of test positivity are shown for microfilaremic subgroups in IgG ELISA (D) and the Ll-SXP-1-RDT (E). In A to D, blue dots represent microscopy results of thick blood smears and orange triangles represent results from leukocyte concentration. In Fig 2A, the negative qPCR Ct values were displayed as a value of 42, which is outside of the detection area. Cut-off values for test-positivity are marked by dashed lines.
Table 3.
A) An overview of ELISA seropositivity and arbitrary units (AU) as well as B) Ll-SXP-1-RDT positivity and absolute intensity of Reader Units (RU) by loiasis subgroups.
*Arbitrary Antibody Units, ** Interquartile range, *** Wilcoxon-rank sum test comparing median AU or RU. ‡Participants were defined by microfilaremia density as low (1–7,999 mf/mL), high (8,000–19,999 mf/mL) and hyper-microfilaremic (≥20,000 mf/mL).