Table 4.
ITNs durability components, outcome measured and analysis method
| Component | Definition | Test conducted | Outcome indicators | WHO criteria or industry standard | Analysis methodc |
|---|---|---|---|---|---|
| Attrition | Net loss from household through discarding or use for alternative purposea | Households survey | Net presence | – | Logistic regression |
| Physical integrity | The physical state of the net to estimate bite protection | Count the number, location and size of the hole(s) of max. 3 nets per household |
The holed surface area is measured by the proportionate Hole Index (pHI)b [44] Median hole surface area (cm2) |
pHI 0–64: good pHI 65–642: damaged pHI ≤ 642: serviceable pHI ≥ 643: too torn or unserviceable |
Negative binomial regression, depending on distribution |
| Functional survival [44] | Estimation of nets still in households in serviceable condition | Presence or absence of net | (Number of nets present and serviceable)/(number of nets originally received and not given away or lost to follow up) | Median net survival in years = time point at which the estimate of functional survival crosses 50% | Logistic regression |
| Biological efficacy | The ability of the net to incapacitate or kill susceptible anopheline mosquitoes after contact with the insecticide | WHO cone/tunnel test using 25 × 25 cm pieces [8] | The proportion of net samples meeting the optimal WHO bio-efficacy criteria | 1 h knock-down ≥ 95% or 24 h mortality ≥ 80% or blood feeding inhibition ≥ 90% | Logistic regression |
| Ifakara Ambient Chamber Test (IACT) using whole nets |
The proportion of mosquitoes dead at 24 h The proportion of mosquitoes not blood-fed |
– | Logistic regression | ||
| Insecticide content | Amount of active ingredients in the net |
Permethrin, Alpha-cypermethrin and piperonyl butoxide: Gas Chromatography with Flame Ionization Detection (GC-FID) Deltamethrin: High-Performance Liquid Chromatography with UV Diode Array Detection (HPLC–DAD) |
The proportion of ITNs meeting with WHO specifications at baseline |
MAGNet: 6 [4.5–7.5] g/kg alpha-cypermethrin Olyset Plus: 20 [15–25] g/kg permethrin; 10 [7.5–12.5] g/kg PBO Tsara Boost: 3 [2.25–3.75] g/kg deltamethrin; 11 [8.25–13.75] g/kg PBO Veeralin 6 [4.5–7.5] g/kg alpha-cypermethrin; 2.20 [1.65–2.75] g/kg PBO |
Descriptive analysis |
aNets that are reported as given away, sold or stolen are not in the denominator (lost to follow up)
bProportionate Hole Index (pHI): the number of holes of each size category measured in the field are weighted by the approximate surface area of the holes to provide a single measure of damage per net
cAnalyses will include product, time point and village. Where more than one net per household is included in the analysis, a random effect for household will be included in the regression model