THE LABORATORY

2. What is the best way to collect the samples in terms of guarantying a good participation and the best positivity rate (early morning collection at home x collection at the field site)? Most surveys collect the first sputum at the field site (on the spot), right after the X-ray is taken and considered to be positive. This sample should be collected under supervision. The second sample is collected in the early morning, immediately after the suspect wakes up, and before he/she engages in any other activity, like having breakfast. The early morning collection represents the pulmonary secretions accumulated overnight, and therefore it usually has a higher positivity. This is even more relevant in a prevalence survey rather than in a clinical setting, because of the bacterial load is expected to be smaller. Patients should be advised to take their samples to the field site / laboratory as soon as possible. If it is considered that it is unfeasible for one or more patients to collect the early morning samples and take them to the field site or to the laboratory (because the suspect lives too far away, for example), then an alternative would be to collect both samples at the field site, in which case it would be best if the collection of the samples was done with an interval of one or two hours in between them. Educational material for patients and field staff with clear instructions and figures explaining the sputum collection procedures should be made available.