Many people in rural communities have rudimentary access to diagnostic testing. Disease misdiagnosis, the inability to monitor long-term illnesses, and poorly trained healthcare workers all contribute to the need to simple, accurate diagnostic methods in rural communities.

The System for Nucleic Acid Purification (SNAP) simplifies sample preparation for such tests. By partnering with local health centers, SNAP can bring cheap and reliable diagnostic testing to the people.

Context[edit | edit source]

This group came together within the 2nd International Development Design Summit to work on a project of importance to the developing world.[1] We collaborated with the Klapperich Laboratory at Boston University who developed a simple method for purifying nucleic acids from samples such as blood or urine.[2] Our team's aim was to create a device that would carry out the process with as little complexity for the user as possible.

SNAP Open blue.jpg

SNAP - First Generation Conceptual Prototype

Introduction[edit | edit source]

Medical diagnostics tools allow the identification and monitoring of illnesses. In many cases, diagnostic tools are vital in order to identify illnesses which do not show symptoms, or for distinguishing among illnesses with common symptoms.[3]

Often, rural people in the developing world do not have adequate access to diagnostic tests. More advanced health centers tend to be in urban areas where there are enough people to justify the expense of hiring trained people and buying the equipment needed for testing. For example, our Guinean teammate Lamine has access to some tests only in the capitol city of Conakry, which is almost 900km from his village. The expense of traveling to a city for medical diagnostic testing can be high, and the work time lost in travel can also be an economic hit.[4]

Many new diagnostic tests are currently being developed to address the diagnostic needs of people in rural areas. Easy-to-use tests enable low-trained people to get accurate results, and quick, portable tests allow healthcare workers from urban areas to travel to these rural areas and quickly run the necessary tests.[3]

The system for nucleic acid purification (SNAP) pictured above provides another tool to increase rural access to diagnostics. The machine simplifies sample preparation for tests based on nucleic acids. By partnering with local health centers and developers of nucleic acid-based diagnostic tests, SNAP can give low income and rural communities access to more sophisticated tests that are simplified enough to be easy to use in the field—enabling more people to benefit from medical diagnosis - and ultimately helping to save lives.

Current Diagnostic Testing in the Developing World[edit | edit source]

The Need for Suitable Diagnostic Testing[edit | edit source]

Diagnoses of suspected illnesses and diseases are often made based on the patient's symptoms. This approach is reasonable if a disease has clear and distinctive symptoms or if the exact cause does not matter as much as treating the symptoms. However, diseases that do not show clear or distinctive symptoms cannot be accurately diagnosed soley through analysing how the patient feels.

When a maleria case is suspected but not confirmed (due to the inavalability of suitable diagnostic testing), the World Health Organisation recommends that drug treatment should still commence. This often leads to the use of expensive maleria drugs when it is not necessary, and also exposes misdiagnosed patients to the risk of side-effects from these drugs.[5] Easily-available and inexpensive diagnostics could help to prevent this occuring.

The use of diagnostic testing is also highly useful for for syphilis. Syphilis is an example of a disease that might not show symptoms in women, but if a woman with syphilis becomes pregnant, it significantly increases the chances that the baby will be stillborn.[5]

Molecular Diagnostics[edit | edit source]

Laboratory diagnostic tools are important for identifying and monitoring illnesses. There are many different kinds of diagnostic tests. For bacterial infections, traditionally, one grows a culture and then identifies the pathogens visually using a microscope. This requires a skilled user for microscopy and equipment and infrastructure such as a microscope and fridge and a regular electrical connection. Cultures can take from several days to weeks to be effective. If people are coming from far away to get tested, they may not be able to come back again later for results.

The next generation of tests used now search for antibodies that one's body creates in response to an infection by a particular type of pathogen. Antibody tests require less skill and equipment in the lab. they can also be packaged into very easy and cheap portable tools, such as strip tests, making them a good choice for the developing world.[6] Many of this kind of simple protein based tests, however, give simple yes or no responses to the presence of pathogens, meaning that one cannot monitor the progression of an illness or distinguish between past and present infections. Additionally, antibody tests cannot distinguish among different strains of the same illness.

Molecular diagnostics are based on identification of the DNA or RNA of a specific pathogen. These tests are quantitative and can differentiate between current and past infections. They can also distinguish among different strains of same infection. With increased drug resistance, this is an important capability. More virulent, multi-drug resistant strains of illnesses can be identified straight away, so that the appropriate, intensive treatment can be given. This type of testing is not used often in rural or underdeveloped areas because traditional methods require expensive equipment and training.

The SNAP nucleic acid extraction machine, however, makes sample preparation for these tests quick and simple. The preparation can be done in the field and the purified nucleic acids can then be transported to the higher level labs. It is easier to transport nucleic acids than blood because the latter needs more temperature regulation and can be more dangerous to transport as infectious diseases can be passed through blood but not through nucleic acids. Also, if the SNAP machine can be coupled with a nucleic acid amplification test (NAAT), it can allow healthcare workers with less training to carry out more sophisticated tests in the field. Research on such technological couplings is on-going.

For further information, see the Appropedia page on Medical Diagnostic Testing in the Developing World.

How the SNAP Process Works[edit | edit source]

The process involves pushing a sample from the test subject, a chaotropic (cell breaking) buffer, ethanol and water through a narrow tube. The sample can be blood, urine or some other source of nucleic acids. The chaotropic buffer is used to denature the cell membrane, freeing the nucleic acids from the rest of the cell. The natural negative charge of the nucleic acids allows them to bond to the positively charged silica particles lining the interior of the tube. Ethanol flushes away the other parts of the cell which are not bond to the tube. Finally, high purity distilled water is run through to dissolve the nucleic acids into a collection chamber. The SNAP machine has a simple interface to do these steps.

This process is able to separate out and purify nucleic acids from all types of viruses, gram negative bacteria, and parasitic pathogens. In its current state, it does not work for Gram positive bacteria. See below for details of the device mechanisms.

Understanding the Market[edit | edit source]

Research into the area of diagnostic testing in the developing world gave three main issues that we felt we needed to address.

Use by low-trained Personal[edit | edit source]

If this device is to be used by local volunteers, the process needs to be simple and unambiguous. Some of the people using this device may be medically trained, however, many people will be relatively untrained health volunteers. Therefore, we are aiming to have this device easy enough to use for anyone who have finished high school, or has a comparable level of education.

In many parts of the world, it is particularly important to have a simple-to-use device because many health professionals are not particularly skilled. For example, high levels of corruption in some parts of Africa means that, a person who is intellectual but doesn't have a health education can become a doctor quite easily if they have friends or parents who works in the health sector[4]

Biohazardous Waste in Developing Countries[edit | edit source]

Waste disposal in many developing-country clinical facilities is often rudimentary – for example, any supplies such as syringes are often recycled either back into the clinic or even into the market as toys for children.[7]

All biohazardous materials from the device must be safely and securely contained, and disposed of suitably. Lancet needles should be retractable or covered after use so as to reduce the risk of infection. Everything that is used for the patient should be used only once, to prevent spread of HIV and other diseases. The use of an incinerator at the health facility can reasonably cheap to use, and is generally suitable to use for disposal of biohazardous waste.

The device as part of a larger supply chain[edit | edit source]

This device needs to be considered as part of a larger supply chain. For the device to be useful and to be used, a number of criteria need to be fulfilled. There must be a reliable supply of reagent packs and other disposables available to the laboratories, as without sufficient disposable materials the device is useless. There will also need to be a network to allow the samples to be delivered to the laboratory for diagnosis, and the results then returned to the health worker in the community. The diagnosis results must be confidential, as in many cases, if a person is known to have a particular disease (such as HIV), they can become alienated by the community.

The regent packs should have a long shelf life, and be stable at room temperature. The other disposable parts (the lancet, straw, and waste and sample containers) must also be readily available. If possible, the device should be designed so that the lancet and the waste and sample containers can be purchased locally if necessary.

Design Requirements[edit | edit source]

Using the project aims and requirements, the folloing design requirements were identified:

Design Criteria How to implement?
Ease of use The device should be useable by non-medically trained personal Minimise the number of steps required by the user.

Make the device simple and obvious to use – for example, by indicating clearly where the user should press or put their hands.

Ease of use The device should be useable by non-medically trained personal Minimise the number of steps required by the user.

Make the device simple and obvious to use – for example, by indicating clearly where the user should press or put their hands.

Short processing time The device should be able to process a sample within 30 minutes (and shorter processing times are beneficial) Higher air pressures will allow shorter processing times, however higher pressures will require high-spec seals and materials.
Low cost The device should cost around $30 USD (not including disposable parts)
Fail-safe If the device breaks, then all biohazardous materials must be safely and securely contained. The parts of the device containing biohazardous materials must be strong.
Robust The device should be suitable for use in the field. Device should be able to withstand mild knocks, be water-resistant, and potentially be tamper-proof.
Size and Weight The device should be suitable for carrying in a rucksack Weight < 3kg, Size < 0.3m x 0.3m X 0.2m (approx)
Adaptable Ability to use a local bicycle pump or electrical pump if available. The air valve should be universal or come with adapters.
Ease of sourcing disposable parts All disposable parts (e.g. lancet, collection vials) must be easy to source and if possible, should be available locally. Use cut-away foam so that each user can adapt the collection drawer to his type of sample collectors.
Long-shelf life and robust reagents Any parts with a finite shelf life should have a minimum life of around one year, and the reagents should be able to withstand changes in temperature.

The Design[edit | edit source]

After analysing the mechanical process and the user needs, a cylindrical rotating device was designed. The product was designed in such a way to limit user error and reduce biohazard. The 1st Generation SNAP Design can be seen here:

Snap design app.jpg

Next Steps[edit | edit source]

To further the project, over the next year, the Team plan to:

  • Undertake further research and field work to further define the needs of rural communities and potential markets.
  • Continue design work with the Klapperich Laboratory to finalize the first generation prototype.
  • Investigate further into low-cost technologies for molecular diagnosis and the feasibility of pairing these with the SNAP device.

Challenges that are still being addressed include:

  • cheap and effective sealing options for the unit
  • design of the reagent blister pack
  • air filter design (if needed)
  • manufacturing considerations
  • packaging and potential "kit" assembly
  • disposal of biohazard waste
  • user interaction

Contact details[edit | edit source]

The SNAP Team can be contacted at Please feel free to get in touch with any feedback or questions.

References[edit | edit source]

  1. International Development Design Summit,
  2. Klapperich Laboratory,
  3. 3.0 3.1 Nucleic Acids Research, 2000, Vol. 28, No. 12, http://www.rapid‐, 10/08/2008
  4. 4.0 4.1 Lamine Dakote, IDDS, 07/27/2008
  5. 5.0 5.1 Nature Reviews: microbiology, Volume 2, March 2004, pp231
  6. Rapid Diagnostics, http://www.rapid‐, 12/08/2008
  7. Mark Koska, WHO, 2008
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Authors Hayley Sharp, zubaida bai
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Language English (en)
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Created July 30, 2008 by zubaida bai
Modified April 30, 2024 by Kathy Nativi
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