The Resistance to Damage (RD) Score Calculator

The Resistance to Damage (RD) Score Calculator is an app designed to calculate both the RD score (formally known as the wRD) and the old RD (oRD) score. These are composite metrics used to assess and summarize the physical durability of bednets, providing valuable insights into the factors that contribute to their resistance to damage.

The Resistance to Damage (RD) Score Calculator

The old RD score was first introduced in 2021 as a way to predict the lifespan of ITNs1-5. Recent analysis of field data has refined the RD score, providing a weighted RD score (wRD)6, which has greater predictive power of field life.

 

The oRD score is calculated using four physical factors of the net that are weighted equally, while the RD score favours hole enlargement and removes abrasion resistance from the calculation:

  • Snag Strength: The force (in Newtons, N) required to break a yarn in the bednet.
  • Burst Strength: The pressure (in Kilopascals, kPa) needed to burst the bednet fabric.
  • Hole Enlargement: The size of the hole (in mm) formed after subjection to a standardized burst test.
  • Abrasion: The number of rubs required to cause yarn breakage and create a hole of at least 5 mm in diameter (needed only for RD score calculation).

App Instructions

1. The starting point of the app is always to calculate the RD score (formally known as wRD). If you want to calculate the oRD score, please select the other sheet at the top of the page.

2. Enter all three variables into the app (four variables for oRD), along with the bednet ID.

3. Press the ‘calculate’ button to generate the RD score. The results will be displayed in both a chart and a table.

4. You can continue to add more bednet IDs with their respective variables, and the app will update the outputs for comparison.

5. The data table can be exported as an Excel file using the ‘Data Extract’ button.

References

  1. Wheldrake A, Guillemois E, Chetty V, Kilian A, Russell SJ. Development of a single resistance to damage metric for mosquito nets related to physical integrity in the field. Malar J. 2021; 20:46.
  2. Wheldrake A, Guillemois E, Arouni H, Chetty V, Russell SJ. The causes of holes and loss of physical integrity in long-lasting insecticidal nets. Malar J. 2021; 20:45.
  3. Wheldrake A, Guillemois E, Arouni H, Chetty V, Russell SJ. Textile testing to assess the resistance to damage of long-lasting insecticidal nets for malaria control and prevention. Malar J. 2021; 20:47.
  4. Wheldrake A GE, Russell SJ. Standard Operating Procedures (SOPS) for the Assessment of Snag Strength Hole Enlargement Resistance and Abrasion Resistance. NIRI, 2020.
  5. Kilian A, Obi E, Mansiangi P, Abílio AP, Haji KA, Guillemois E, et al. Correlation of textile ‘resistance to damage’ scores with actual physical survival of long-lasting insecticidal nets in the field. Malar J. 2021; 20:29.
  6. https://www.biorxiv.org/content/10.1101/2025.03.02.641027v1