Objective: To explore factors influencing the results of in vitro microtest for drug sensitivity of Plasmodium falciparum (Pf).
Methods: Handy media, microplates predisposed with antimalarial drug, cultured Pf parasites (FCC-1/HN isolate) and blood samples from patients were used to evaluate the factors influencing the in vitro determination of drug sensitivity of Pf.
Results: Liquid medium and lyophilized medium stored at 4 degrees C for 2 months and 1 year respectively could keep their effect unchanged. The effect of the drug-coated plates was not changed within the following period of storage: plates coated with chloroquine and piperaquine stored at 4 degrees C for 2 years and 6 months respectively; plates coated with pyronaridine and artesunate stored at 4 degrees C for 3 months. The adhesive paper of the sealed plate could be unsealed once only. The plastic plate must be harmless to the growing of parasites. The drug liquid should not be stored over 2 wk at 4 degrees C; otherwise the drug concentration was changed. Parasites tested were at synchronous ring stage, with a density of 1,000-80,000/microliter blood, stored at room temperature for 1 h, and at 4 degrees C for 48 h. Operation needed to follow strictly the standard technical procedure.
Conclusion: Drug plates, media, adhesive paper, parasites and operation technique can affect the result of in vitro microtest for drug sensitivity of P. falciparum. Standardized materials and operational procedure should be used to guarantee a reliable result of the test.