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Oral Rehydration Salts (ORS)

ORS is a sugar and salt mixture that is dissolved in water and administered orally to prevent dehydration as a consequence of diarrhea.

Unit of intervention 1 sachet (21 grams)

Formula

Treatment course for an episode of diarrhea 2 sachets

Target population Children under five with diarrhea

For more information about how PSI is increasing access to ORS to improve health and save lives, visit our website at:
http://www.psi.org/health-area/child-health/diahhreal-disease/

Model Overview

PSI’s ORS impact model is based on the Lives Saved Tool (LiST). LiST is used to estimate the number of deathsa verted with complete coverage of ORS for treatment of diarrhea among children under age five in a country. This number of deaths averted at the population level is translated to deaths averted per sachet of ORS, using baseline coverage of ORS, the number of ORS sachets needed per episode of diarrhea, and diarrhea incidence rates. Once we have deaths averted per sachet of ORS, we apply data from the 2010 Global Burden of Disease study to estimate the corresponding number of DALYs averted.

Model Outputs (impact metrics)

Estimates of DALYs averted, deaths averted, CYPs provided, and unintended pregnancies averted represent the projected health impact of the intervention. It is projected because it has not been directly measured.

Examples based on distribution of ORS sachets in Myanmar in 2015 Statement of modeled results, examples:

In 2015, an estimated 3 deaths and 279 DALYs would be averted if 10,000 sachets of ORS were distributed in Myanmar.

For more details about how PSI models the impact of ORS, see below.

Model Details

Step 1: Running a projection in the Lives Saved Tool (LiST)LiST is a multi-cause mortality model developed by Johns Hopkins Bloomberg School of Public Health that estimates the number of deaths averted (or lives saved) through the scale up of maternal and child health interventions.

PSI begins by running a projection in LiST for a selected country. In this projection, coverage of ORS is increased from the current, country-specific baseline to 100% among children under five. LiST then projects the number of deaths averted by this increased level of coverage.

Step 1 Output:
Number of additional deaths averted (or lives saved) among children under five if coverage of ORS is increased from baseline to 100% in select countries

Step 2: Estimating deaths averted per unit of ORS (deaths averted coefficient)PSI uses the step 1 output (deaths averted at 100% coverage of ORS) to determine the number of deaths averted by a single sachet of ORS. To do this, we divide the number of deaths averted at 100% coverage by the number of ORS sachets needed to reach 100% coverage.

PSI estimates the number of ORS sachets needed to reach 100% coverage using a number of parameters, including baseline coverage of ORS, the number of ORS sachets needed per episode of diarrhea, and diarrhea incidence rates. Each case of diarrhea is assumed to require two sachets of ORS. We also account for wastage of ORS sachets in the supply chain, assumed to be 10%.

Step 2 Output:
Deaths averted coefficient

Step 3: Estimating DALYs averted per unit of ORS (DALYs averted coefficient)A DALY (or disability adjusted life year) includes two components: years of life lost due to premature death (YLL) and years lived with disability (YLD). DALYs averted are in turn comprised of YLLs averted and YLDs averted or, put simply: death and disability that is prevented by PSI interventions.

To estimate YLLs averted per unit of ORS, PSI first determines the number of years of life lost per diarrhea death among children under five in a selected country. This is equal to the life expectancy at the average age of death from diarrhea. Age specific life expectancy is taken from the 2010 Global Burden of Disease study (GBD 2010). The number of years of life lost per diarrhea death is then multiplied by the number of deaths averted per sachet of ORS (deaths averted coefficient), calculated in step 2 above for a selected country. This gives us the YLLs averted per unit of ORS.

To estimate YLDs averted per unit of ORS, we use a YLD/YLL ratio, based GBD 2010. This ratio represents the relative number of years lived with disability for every year lost due to death from diarrhea in a selected country. We apply this ratio to the number of YLLs averted per sachet of ORS to determine the number of YLDs averted per sachet. Because ORS treats diarrhea, rather than prevents it, we assume that individuals will still suffer some disability before and during treatment. Therefore, we only include half of the total YLD averted in our estimate. This is a standard assumption in all of our treatment models.

Finally, YLLs averted and YLDs averted are added together to determine the number of DALYs averted per sachet of ORS.

Step 3 Output:
DALYs averted coefficient