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[PHNOM PENH] A 'cool box' developed in Cambodia uses an age-old principle to keep rapid diagnostic tests (RDTs) for malaria cool in remote clinics, say researchers.

Clinics in Cambodia where microscopy is not available are increasingly using RDTs to diagnose malaria.

But temperatures in clinic storerooms can reach up to 42 degrees Celsius — much higher than the 2–30 degrees Celsius recommended for storage — and electricity supplies are often unavailable or not reliable enough for storing tests in fridges.

RDTs become less sensitive and stop working sooner if they are not stored at the correct temperature and humidity.

In research published in Malaria Journal last month (23 January), the boxes were found to extend the lifespan of RDTs.

The 24-litre boxes are made by the Cambodian National Center for Parasitology, Entomology and Malaria Control (CNM) from one millimetre-thick iron sheeting. A tray in the top holds nine litres of water which is drawn into a cotton outer layer.

They remain cold by evaporative cooling, in which water in the damp cotton takes in heat as it evaporates, cooling the metal sides. The same principle has long been used to keep food and water cool in the tropics and sub-tropics.

Researchers installed the boxes in clinics in Battambang province and routinely measured the temperature and humidity inside the storerooms and the boxes. RDTs stored in the boxes were periodically removed for testing.

The boxes kept the temperature below 30 degrees Celsius on all but a few occasions. RDTs that had been stored in the storerooms stopped working after 210 days but those kept in the cool boxes gave correct results for 360 days.

Duong Socheat, advisor to Cambodia's Ministry of Health and director of CNM, said that about 2,000 cool boxes have been distributed to remote clinics in 20 provinces. They cost between US$60 and US$80.

He said that the boxes could extend remote communities' access to other perishable diagnostics and medicines.

Yok Sovan, a malaria researcher within the Ministry of Health, said that Cambodia has decided to use this old technique now because it simply cannot afford to buy modern materials such as fridges in which to store diagnostic kits and drugs in remote areas. The researchers said that this is the first time the technique has been used for public health on a large scale.

Sovan told SciDev.Net that the technology could be used in neighbouring countries such Laos, Myanmar, Thailand and Vietnam.

Link to full article in Malaria Journal