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Table 3 Number and proportion of Olyset nets of different ages with recommended permethrin content and passed WHO cone/tunnel tests criteria

From: Durability of Olyset campaign nets distributed between 2009 and 2011 in eight districts of Tanzania

Explanatory variables Net age (months) ( %)
≤25 26–36 37–48 >48
Number of sub-sampled nets 48 (24) 106 (54) 27 (14) 17 (8)
Cone assay
 Proportion of nets passed WHO cone assay criteriaa 30 (62) 64 (60) 20 (74) 12 (71)
Pass WHO cone or tunnel testsb
 Proportion of nets passed WHO cone or tunnel tests criteria 45 (94) 105 (99) 27 (100) 17 (100)
Chemical residue
 Proportion of nets with recommended permethrin content 41 (85) 86 (81) 20 (74) 8 (47)
 Mean permethrin content in g/kg (95 % CI) 16.8 (16.3–17.2) 16.8 (16.4–17.4) 16.5 (15.7–17.3) 14.0 (12.0–16.0)
  1. a WHO cone assay criteria: ≥95 % knockdown and/or ≥80 % mortality pass rate
  2. b WHO tunnel test criteria: ≥80 % mortality and/or ≥90 % blood feeding inhibition pass rate