Home Malaria Test Kit Called Malaria Rapid Diagnostic Test (MRDT)

Malaria is a disease cause by five specie of plasmodium. It's vector is the female anopheles mosquito. It is a deadly disease with high mortality rate. Malaria is an endemic disease common in the tropics. It is very common in places like Africa, Asia and South America with tropical climate. The signs and symptoms vary from one or more sign and symptoms like chills, fever, vomiting, diarrhea, etc. Unfortunately, these signs and symptoms are not peculiar to malaria alone. This makes diagnosis using just the signs and symptoms difficult. The only way to diagnose malaria is the use of microscopic assay. However, microscopic assay is not readily and easily available in many part of the country. That is why a malaria rapid diagnostic test (mRDT) is a savior.
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It was a standard some years ago to treat persons with one or more of the signs and symptoms mention above. This is because malaria was the major disease responsible for many sickness then. However, with improve adoption of preventive methods, improve standard of living the number of malaria infection is reducing. This means that just treating malaria may not yield positive results. Such indiscriminate use of antimalarial can lead to development of drug resistance. The best thing to do is to exclude malaria infection before treatment. The only way to do it is to carry out a test.
Microscopic assay involve the use of microscope to view a thin film of blood over a slide using a 100x lens. The number of visible parasite is counted. The result is recorded. This takes within some few minutes. But when this is not available, mRDT can be use.

Malaria Rapid Diagnostic Test (mRDT)

This test make use of the principle of conjugation of two compounds with affinity for each other. It is called antibody/antigen complex. The resultant complex forms a color that is visible to the eyes.
There are different types of mRDT kits available but all have the same working principle. The major difference is the antigen they detect and the type of specie. Since plasmodium falciparum is the most prevalent in Africa, majority of the test kit will be those that will detect it and maybe any other one. Some detect more than one type of specie.

Working Principle Of mRDT

All plasmodium species produce proteins called antigens. The test kit detects the presence of these antigens. The test kit come in card, dip stick, hybrid cassette or plastic cassette. They are coated with dye labelled antibody specific for a target malaria parasite antigen at the top. The length of the test kit is plated with a chromatographic material. Toward the end side is a test line coated with antibody also specific for the target antigen. The control line is coated with antibody specific for labeled antibody or antigen. Three antigens commonly target are:
1. Histidine rich protein 2 (HRP-2): this is specific for only p. Falciparum and it is found at the asexual stage of the gametophyte.
2. Parasite specific plasmodium lactate dehydrogenase (p. Falciparum specie, pan and p. Vivax specific (enzymes found in the glycolytic pathway of the parasite)
3. Parasite aldolase (pan specific) also an enzyme found in the glycolytic pathway of the parasite.
For test kits that have more than one antigen, there is usually about three lines. The first one if for one antigen detection, second one is also for another antigen while the third is the control.

MRDT Kit

The complete Kit comes with the test device (cassette, etc), assay diluent, disposal lancets or needle, alcohol or methylated spirit, manual, and other peripheral not really important.

Malaria rapid diagnostic test device

Before Using MRDT

Be sure the kit was properly stored according to the manufacturer's instructions as wrong storage and usage will render the result invalid. Some do well between 1-40°c. However, some manufacturer's recommend the temperature be brought to room temperature before use. Some products also come with a humidity detector because they are very sensitive to humidity. A colour change in the detector indicate saturation and which means that the product can no longer be use as it may not give accurate reading.

MRDT Procedure

This test can be done at home even without prior knowledge or the presence of a health care expert.
1. Take out a cotton wool
2. Soak it in alcohol or methylated spirit provided or gotten from a community or retail pharmacy
3. Clean the tip of any finger using the soaked cotton wool
4. Allow the finger to dry
5. Prick the finger lightly with a lancet or needle
6. Drop one or two drops of blood or the quantity specified by the manufacturer into the right well in the test device by gently quizzing the finger
7. Add some drop (or according to the manufacturer instructions) of the diluent provided to the blood well or a second well close to the blood well. The diluent help to lyse the parasite from the red blood cell inside the drop of blood
8. Wait for the result after some minutes according to the manufacturer's instructions

Reading MRDT Result

A visible test line indicate the presence of the parasite. This is because the test line form a parasite antigen+labelled antibody complex which is visible as a coloured line. The control line colour is a mixture of labelled antibody+antibody at the control which shows that labelled antibody are still in the device. The control line is indication that the test is now complete as the blood have move past the test line with the diluent. It also confirm that some free antibodies conjugated with dye are still available in the test device ready to mix with antigen if still available and that the capturing properties of the antibody remain intact. When the test is for more than one antigen, the second test line change colour if there is a parasite in the blood
The intensity of the the test band will vary depending on the number of parasite in the blood because the amount of antigen will increase. This will inversely reduce the intensity of the colour of the control as majority of the labelled dye antibody will be used up to form complex with the high amount of antigen.
When malaria rapid diagnostic test is properly use, the result is more than 95 percent accurate.

Result Interpretation

Negative: the presence of one coloured band at the control line
Positive: presence of two coloured band at the test and control line or three band when the test is for more than one antigen. Two coloured bands in one test line and control line and none in the second indicate the presence of one specie excluding the other
Invalid: if the control line is not visible within the stipulated time by the manufacturer

Disadvantage Of MRDT

Some say every good thing must have at least one disadvantage. This may be true with mRDT kit. A couple of questions have been raised due to some of the problems that have risen since the introduction of this kit.
The test result is only detectable for blood samples with more than 100 parasites per milliliter of blood. Although, recent kits claim to detect as low as 40 parasite per milliliter. This is unlike microscopic assay that can detect as low as 5 parasite per milliliter of blood. This is a big disadvantage because some group of persons come down with malaria symptoms even with such a low level of malaria. This is very common in none immune individuals that have not been exposed to malaria before.
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Another notable disadvantage is that it gives false positive in the presence of autoantibodies such as rheumatoid factor.
That is not all. This test detect the presence of malaria parasite antigen in the body. This include antigen that remains in the body even after two weeks of treatment. This can cause a big problem when a patient takes antimalarial and still treat again because the test shows that the antigen is still in the body which is not an indication that the parasite is still in the body.
Above all, this kit is recommended to be use by individual and better still community or retail pharmacy before prescribing. By doing this, we are helping the future generation in curbing the menace of drug resistance to antimalarial.
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