Assessing the adherence to HWT use- A tricky business

Ghislaine Rosa Environmental Health Group

Department of Disease ControlLondon School of Hygiene and Tropical Medicine University of London

Improving health worldwide

www.lshtm.ac.uk

HWT is a complex process

High adherence is necessary for achieving health benefits

Epidemiological models based on quantitative microbial risk assessment (QMRA) studies have shown that even occasional exposure to untreated drinking-water can largely diminish the potential health benefits of HWT interventions.(Brown & Clasen 2012, Enger et al. 2013, Hunter et al. 2009).

Figure : DALYs averted per 100,000 population, per year, based on assumptions about technology effectiveness (2 log10 reductions in each pathogen class), and varying levels of adherence to HWT and background water quality (Brown and Clasen 2012)

A key measure of interest is thus Adherence to HWT use

• No standard definition of adherence in the HWT literature.

• Paucity of data on adherence to HWT use in the POU evidence base (Clasen et al. 2015).

• No standardised measure or indicators in the HWT research context.

Consistent and correct use of a HWT method over a period of time (Clasen et al. 2009).

Total proportion of treated water out of all water consumed (Brown & Clasen, 2012, Enger et al. 2013).

HWT use is measured in a variety of ways

Self-reported

use

Ask

Observational spot-checks

Look for clues

Availability of treated

water

Test

HWT use is measured in a variety of ways

Self-reported

use

Ask

Observational spot-checks

Look for clues

Availability of treated

water

Test

• Do you usually do anything to your water to make it safer to drink?

HWT use is measured in a variety of ways

Self-reported

use

Ask

Availability of treated

water

Test

• Is there are filter in the households? Is there water in the lower container?

• Are there SODIS bottle on the roof? Are their bottles ready to drink?• Does the household have chlorine tablets?• Is there fuel and a pot for boiling water?

Observational spot-checks

Look for clues

HWT use is measured in a variety of ways

Self-reported

use

Ask

Observational spot-checks

Look for clues

Availability of treated

water

Test

• Is there FCR in the reportedly chlorinated drinking water?• Are there indicator bacteria in the reportedly treated water?

A key measure of interest is thus Adherence to HWT use

• No standard definition of adherence in the HWT literature.

• Paucity of data on adherence to HWT use in the POU evidence base

• No standardised measure or indicator in the HWT research context

Self-reported user

Confirmed-user

Exclusive-user

Current user

Adherence to HWT use: No standardised measure or indicator

RCT, chlorine-based HWT, India (Boisson et al. 2013)Householders who reported their water to be treated with a tablet at the time of visit were defined as reported users while those with detectible RFC in the sample were defined as confirmed users.

RCT, filter-based HWT, Dem. Rep. Congo (Boisson et al. 2010)Participants were classified as current users if they reported using the filter ‘today or yesterday’

and if the field investigator found the filter hung for use with water in the top vessel of the device. Consistency of use was estimated by asking the respondent if he/she had drunk unfiltered water

within the previous day.

RCT, filter-based HWT, Zambia (Peletz et al. 2012)Households were classified as “reported users” if 1) the filter was observed in household at the time of visit, 2) the storage vessel contained water reported to be treated at the time of visit, and 3) the respondent reported using the filter on the day of or day prior to the day of visit. Households were classified as “confirmed users” if, in addition to these three criteria, there was at least a 1 log10 TTC improvement in their stored household water

Longitudinal assessment of HWT use

• Paucity of studies have assessed compliance longitudinally.

• Assessing % of times a household had treated water in 100%, 50%... of all visits.

• Extra layer of understanding (especially among reported users).

Figure: Percentage of total households having boiled water in preparation or available for drinking at the follow up visits. Cambodia, 2011.(Brown and Sobsey 2012).

Concurrent consumption of treated water at home

Even if HWT uptake is high in intervention studies, participants may still consume untreated water, leaving them exposed.

Country HWT method

Uptake Drinking of untreated water

Reference

Democratic Republic of Congo

Water filter 68% of intervention households were classified as current users

73% of adults and 95% of children reported drinking untreated water the day prior to the interview

(Boisson, Kiyombo et al. 2010).

India SODIS 78% - Bottles on roof, 75% Bottles in house

86% of respondent reported that their children drank untreated water

Rose et al. 2006.

India Water filter On average, filters had water in 92.4% of all visits, and 81.2% of respondents reported to drink filtered water at time of visit.

On average 40.1% reported drinking untreated water in previous 24hr, 25% reported doing so at 3 or more of all 4 follow-up visits.

Rosa et al. unpublished.

Concurrent consumption of treated water at home: Over-reporting of good practices

Country Zambia Urban Rural

India Urban Rural

Peru Urban Rural

Main HWT method used

Chlorine Chlorine Filter Chlorine Boiling Boiling

% of participants reporting not to drink untreated water at home

39.7 48.5 4.1 21.9 34.6 67.7

% with untreated water at home (1st assessment)

87.1 40.0 100.0 100.0 94.1 80.0

% with treated water at all 3 collection points

50.0% 13.3% - - 81.0% 42.9%

The household is not the participant’s sole environment

• Little is known about what water participants consume outside of their home.

• Though POU intervention target the household, little attention has been directed at recommendations outside the home.

School Social

Agricultural fields Work

Toolkit for M&E HWTS

• Addresses the need for consistent and harmonised M&E of HWTS interventions

• Core set of 20 indicators

• Grouped according to 6 themes:• Reported & observed use• Correct & consistent use & storage• Knowledge & behaviour• Other environmental health

interventions• Water quality

Toolkit for M&E HWTS

Toolkit for M&E HWTS

Toolkit for M&E HWTS

Recommendations

• Promote the inclusion and reporting of a set of standardised indicators of adherence to HWT in all POU intervention/programs.

• Indicators should be based on combination of self-reported and observed indicators (ideally assessed longitudinally).

• Fine balance should be achieved between repeated assessments and reducing potential of participant reactivity/bias.

• Concomitant consumption of untreated water should be monitored and reported (preferably through longitudinal assessment).

• Guidelines or recommendations should be developed around water consumption outside the home environment.

Thank you!

Longitudinal assessment of HWT use

• Adherence to boiling among 50 HH reporting to “Always” or “Almost always boil their water” (Psutka et al. 2011).

• Overall, 20% of the 1,080 intervention households never had residual chlorine in their child's water during follow-up visits and 76% had chlorine on less than half of the total visits. (Boisson et at. 2013).