Fresh eggs are incubated from the parasite of interest and serial dilutions of the drug of interest are applied. The percentage of eggs that hatch or die is determined at each concentration and a drug response curve may be plotted. The data can then be transformed and analysed to give further statistics such as an ED50.
This technique is labour-intensive, expensive and can take some time, however an egg hatch assay will give and accurate and reliable result.
Jackson, F.; Jackson, E.; Coop, R. L. (2001). "Egg hatch assay for determination of resistance of nematodes to benzimidazole anthelmintics". In Halton, David W; Behnke, Jerzy M; Marshall, Ian. Practical Exercises in Parasitology. pp. 313–20. doi:10.1017/CBO9781139173353.038. ISBN978-1-139-17335-3.
Demeler, Janina; Kleinschmidt, Nina; Küttler, Ursula; Koopmann, Regine; Von Samson-Himmelstjerna, Georg (2012). "Evaluation of the Egg Hatch Assay and the Larval Migration Inhibition Assay to detect anthelmintic resistance in cattle parasitic nematodes on farms". Parasitology International. 61 (4): 614–8. doi:10.1016/j.parint.2012.06.003. PMID22728255.