Is Structured Observation a Valid Technique to Measure Handwashing Behavior? Use of Acceleration Sensors Embedded in Soap to Assess Reactivity to Structured Observation

Structured observation is often used to evaluate handwashing behavior We assessed reactivity to structured observation in rural Bangladesh by distributing soap containing acceleration sensors and performing structured observa non 4 days later Sensors recorded the number of times soap was moved In 45 participating households, the median number of sensor soap movements during the 5 hour time block on pre observation days was 37 (range 0 3-10 6) During the structured observation the median number of sensor soap movements was 5 0 (range 0-18 0), a 35% increase, P = 0 0004 Compared with the same 5 hour time block on pre observation days the number of sensor soap movements increased during structured observation by >= 20% in 62% of households, and by >= 100% in 22% of households The increase in sensor soap movements during structured observation compared with pre observation days indicates substantial reactivity to the presence of the observer These findings call into question the validity of structured observation for measurement of handwashing behavior