The best practice for preparation of samples from FTA (R) cards for diagnosis of blood borne infections using African trypanosomes as a model system

Background: Diagnosis of blood borne infectious diseases relies primarily on the detection of the causative agent in the blood sample. Molecular techniques offer sensitive and specific tools for this although considerable difficulties exist when using these approaches in the field environment. In large scale epidemiological studies, FTA(R) cards are becoming increasingly popular for the rapid collection and archiving of a large number of samples. However, there are some difficulties in the downstream processing of these cards which is essential for the accurate diagnosis of infection. Here we describe recommendations for the best practice approach for sample processing from FTA(R) cards for the molecular diagnosis of trypanosomiasis using PCR. Results: A comparison of five techniques was made. Detection from directly applied whole blood was less sensitive (35.6\%) than whole blood which was subsequently eluted from the cards using Chelex(R) 100 (56.4\%). Better apparent sensitivity was achieved when blood was lysed prior to application on the FTA cards (73.3\%) although this was not significant. This did not improve with subsequent elution using Chelex(R) 100 (73.3\%) and was not significantly different from direct DNA extraction from blood in the field (68.3\%). Conclusions: Based on these results, the degree of effort required for each of these techniques and the difficulty of DNA extraction under field conditions, we recommend that blood is transferred onto FTA cards whole followed by elution in Chelex(R) 100 as the best approach.