Comparative detection of trypanosomal DNA by loop mediated isotherma amplification and PCR from FTA cards spotted with patient blood

We analyzed DNA eluted from FTA (Flinders Technology Associates) cards spotted with blood from Human African Trypanosomiasis (HAT) patients admitted at Lwala Hospital, Eastern Uganda, and Kaliua Health Centre in northwestern Tanzania. The aim was to evaluate Loop mediated isothermal Amplification (LAMP) for detection of trypanosomal DNA in clinical samples, and to characterize the infecting trypanosomes to sub-species level. LAMP targeting the Trypanozoon conserved Random Inserted Mobile Element (RIME) and that for the SRA were performed. For comparison, PCR for the Serum Resistance Associated (SRA) gene specific for T. b. rhodesiense and that to amplify the T. b. gambiense specific surface glycoprotein (TgSGP) were done. Out of 128 samples analyzed, SRA-PCR was positive in 101 (78.9% sensitivity; 95% Confidence Interval, CI of 71.1-85.1%), the SRA-LAMP positive in 120 (93.8%, 95% CI= 88.2-96.8%), while RIME-LAMP revealed signals in 122 (95.3%; 95% CI=90.2-97.8%). RIME- and SRA-LAMP were each significantly more sensitive than SRA-PCR (P=0.000 and P=0.001 respectively, Fisher's exact test). There was poor agreement with SRA-PCR, yielding Kappa values of 0.31 and 0.40 respectively. Agreement between SRA-LAMP and RIME-LAMP was almost perfect (Kappa= 0.85; 95% CI=0.64-1). All the 128 field samples were negative for the TgSGP-PCR. Blood spots from 3 T. b. gambiense HAT cases from NW Uganda were positive by TgSGP-PCR and RIME-LAMP. PCR took 5 times longer to execute than LAMP. LAMP may be useful to monitor for emerging HAT foci, or test travellers returning from endemic countries. It should be evaluated in a case-control study to determine its utility as a HAT diagnostic