Table 1 Sources of variation in Kato-Katz (KK) and qPCR measurement of helminth eggs in stool

Biological

Worm burden of host and per-worm egg output [49, 53, 54]; Stool volume and consistency [55, 56]; Egg clumping [21, 22, 57]

Same as shown at left for KK

Technical

Slide readability, technician’s skill [20, 56]; Degradation of eggs on slide over time (particularly important for hookworms) [22, 58, 59]

Efficiency of DNA extraction [26, 27]; Pipetting error [28]; Target and primer DNA sequences [24]; Reaction conditions