Diagnostic Blood Test: Malaria in Nepal and India

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QUESTION

My daughter has returned from a 6 week trip to Nepal and then India. About 20 minutes into the flight home she developed pains and aches in her hips and legs, fever, generally feeling dreadful but no nausea or diarrhea. When she arrived after the 10 hour flight her temperature was 100.5. We were concerned about malaria, but when she saw her primary care doctor the next morning she felt much better and her temperature was normal.

Blood taken at that visit showed no sign of malaria, but the doctor said that she could develop a recurrence in 3-4 weeks time when blood test should be repeated to confirm malaria if present.

I don’t doubt her doctor, but do these symptoms suggest malaria? How common is it for an initial episode of malaria to show up as negative on blood tests? She started taking tablets 3 days before entering a high risk area and took them for 3 weeks, but stopped during a brief diarrheal illness and did not restarted her anti malaria tablets.

ANSWER 1 – From Malaria.com Editor:

I think your GP might be mistaken about this – the only way to diagnose malaria is through a blood test which is positive for the disease! I have never heard of any cases where the initial blood test is negative, followed by a positive recurrence several weeks later. There are cases were the initial level of infection is quite low, in which case sometimes the parasites can be missed when looking at the blood film; however, when symptoms are present, this is rare. Moreover, there is no biological reason for a recurrence in several weeks; usually, reoccurrence occurs when treatment is given and for whatever reason is unsuccessful, allowing the malaria parasites to come back (and this assumes they are positively observed in the first place!).

Another diagnostic option, if you want to double check, is to see if you can find a rapid diagnostic test for malaria, which uses a drop of the patient’s blood to look for proteins produced by the malaria parasite. Similarly, there are tests which look for antibodies against malaria; this kind of test, known as serology, is not good for diagnosing active infections since antibodies can persist after the infection has been cleared, but may give you an indication of whether your daughter was exposed to malaria at all during her time in Nepal. Both of these are even more sensitive than blood smears, and although not as common as blood smears, are available in many places, particularly through hospitals which have tropical medicine departments or experts. All in all, if your GP is insisting on a second malaria test in a few weeks, by all means there is no harm in doing that, but in the meantime I would seek a second opinion since I think it is more likely your daughter has another infection (possibly a gastrointestinal bug, or a viral infection) which may risk going undiagnosed if your GP fixates on malaria as the answer.

Regarding the symptoms, unfortunately the symptoms of malaria are very general and it is almost impossible to accurately diagnose the disease on the basis of symptoms alone, hence why a blood test is so important. The blood test, with positive observation of the malaria parasites, is also crucial to determine which species of malaria the patient has, which may have implications for the appropriate treatment.

Answer 2: From Malaria.com Medical Advisor (MD)

The diagnosis of malaria should always be considered for patients with a fever who have traveled to malaria endemic areas. Your concerns that this may be malaria are well founded. Malaria symptoms in the first few days of infection are similar to the early stages of many other febrile illnesses, including viral and bacterial infections. In malaria, the fever also typically waxes and wanes in the manner you described. Confirming the diagnosis requires detecting parasites or their products in a blood sample. The most common test involves inspecting blood under a microscope for the presence of malaria parasites. Sometimes early in the disease there aren’t enough parasites for detection by this method. For this reason, several blood smears taken at 12-24 hour intervals are sometimes required to rule out a diagnosis of malaria in a symptomatic patient.

Additionally, your daughter was vulnerable to infection because she stopped taking antimalaria medicines while traveling in a region of malaria risk. To offer protection, these medicines must be taken for the duration of the stay, and depending on the medicine, up to 4 weeks after the last possible malaria exposure.

Unfortunately most medical doctors in regions where malaria is very rare, like the the United States and Europe, have little experience diagnosing and managing malaria. I would advise you to seek attention at a travel clinic or infectious disease specialist without delay, where it is likely further blood tests will be undertaken immediately to establish laboratory confirmation, and the prompt initiation of treatment for malaria if present.

High Count of Malarial Antibodies

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QUESTION

In 2007 we travelled to Kenya and Zanzibar. We took the normal anti-malarial tablets and were unaware of having been bitten. My older son has recently had a full medical and one of the blood tests which he had to repeat came back with a high count for malaria antibodies for Plasmodium falciparum. The doctor told him that he had had malaria at some time. We are puzzled as he has never been ill since returning. Can this happen? On the other hand my younger son has not been fully fit since returning from the trip, flu like symptoms, lack of energy etc. He has had several blood tests including one for glandular fever but nothing has shown up. Should he be tested for malarial antibodies? Could this be the reason he has had recurrent bouts of illness.

ANSWER

It is certainly possible to be exposed to malaria, but for your body to successfully fight the infection before it can reproduce and establish, thus the person will never experience the full illness. This is likely what happened with your elder son. As for your younger one, malaria tends to be an acute illness rather than a long-lasting chronic one, particularly the types of malaria that are found in East Africa.

Since your elder son was exposed and seems to have antibodies to malaria, I don’t think an antibody test will be particularly illuminating with regards to diagnosing your younger son. It would be better to have the doctors test him for malaria using the traditional thick and thin blood smears, which are then looked at under the microscope. This test will better inform the doctors whether your son has an active malaria infection, and will also be able to determine the species of malaria he has (if positive), and thus what treatment would be most effective for him. Again, though you should do this test to rule out malaria for sure, I think it is unlikely that your son has been experiencing symptoms caused by malaria for this length of time.

Can’t Get Rid of Malaria

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QUESTION

Each and every month I am suffering from malaria ..Treatment is also going on but I am unable to get rid of it.

ANSWER

It is very unusual to be reinfected so constantly with malaria. First of all, how are you getting diagnosed? You should be getting a blood test, and not relying on symptoms only; the symptoms of malaria are very general and it could be that you are suffering from something else entirely. The two main methods for accurate diagnosis are blood smear and rapid diagnostic test. The blood smear is used throughout the world, but can sometimes miss light infections (though if you feel sick, your infection is likely heavy enough to be detected by this method). The problem is that it requires a trained technician to take the sample, prepare it properly, and read it thoroughly and accurately. In my experience, many clinics, especially if they are rushed and busy, will not take the time to read a blood slide properly, and will just diagnose malaria without looking. This is really bad! It is very important to be properly diagnosed, so you can get the correct treatment, and if you don’t have malaria, you can be diagnosed for something else. The second kind of diagnostic is a rapid diagnostic test, or RDT. This looks for antibodies to malaria in your blood, and is very sensitive and quick. In an ideal world, you should try to have both done, to cross-check the results.

The next thing is to check whether you are receiving the correct treatment for the type of malaria that you have (if you are positively diagnosed with malaria). In many parts of the world, malaria has become resistant to some of the main medications used against it. Notably, this is the case in many places with Plasmodium falciparum, the most dangerous kind of malaria, which has become resistant to chloroquine in many parts of the world, to sulfadoxine-pyrimethamine (sold as Fansidar in many places) and also to mefloquine (sold as Lariam) in some places. As such, the World Health Organisation NEVER recommends these treatments be given as first line drugs against P. falciparum malaria – instead, they recommend artemisinin-combination therapies (ACTs), such as Alu, Coartem or Duo-Cotecxin. If you have been diagnosed with P. falciparum, you must try to take these kinds of drugs first. No resistance to ACTs has been reported, so if you take the full dose correctly, as prescribed by your doctor (and check to make sure the drugs are not expired), then you should be cured of malaria.

However, treatment does not stop you from getting infected again, and this is where prevention comes it. Preventing malaria is a cornerstone of control efforts. Since malaria is transmitted by a mosquito, preventing mosquitoes from entering the house, and particularly stopping them from biting you at night, is crucial. Screening all doors and windows can help stop mosquitoes from getting in, and in high transmission areas, many people will also spray inside their houses every once in a while with insecticides to kill any lingering insects. In addition, sleeping under a long-lasting insecticide treated bednet can drastically reduce the number of mosquitoes that are able to bite you at night. If you already have a net, it may be worth re-dipping it in insecticide (usually permethrin) to make sure it is still working effectively. The mosquitoes that transmit malaria feed at night, so if you are walking around outside in the evenings or at night, it is important to try to wear long-sleeved clothing, to prevent them from accessing your skin. All of these efforts will help prevent you from getting malaria again in the future.

Blood Smear Technique

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Blood films are made by placing a drop of blood on one end of a slide, and using a spreader slide to disperse the blood over the slide’s length. The aim is to get a region where the cells are spaced far enough apart to be counted and differentiated.

The slide is left to air dry, after which the blood is fixed to the slide by immersing it briefly in methanol. The fixative is essential for good staining and presentation of cellular detail. After fixation, the slide is stained to distinguish the cells from each other.

Source: Wikipedia (http://en.wikipedia.org/wiki/Blood_film)

Diagnostic test for malaria?

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QUESTION:

What are the possible diagnoses tests?

ANSWER:

A blood test is usually required to diagnose malaria, although the blood can be used in a number of different ways. The most common, traditional form of diagnosis is a blood smear, observed under a microscope by a qualified technician. These can be “thick” or “thin”; the “thick” smear examines a whole drop of blood for the presence of the malaria parasites infecting the patient’s red blood cells. Because a relatively large volume of blood is examined in this way, the thick smear is useful for detecting low levels of parasites in the blood, and therefore is good for an initial “positive or negative” diagnosis. The thin smear allows for a closer look at the infected blood cells, and thus can be used to identify the species of malaria, which can be important for giving the patient appropriate treatment. The danger with blood smears is that very low intensity infections can sometimes be missed, given the a low number of parasites in the blood.

More recently, a number of antibody tests have been developed to test for malaria. These so-called “rapid diagnostic tests” (or RDTs) do not require the expertise of a blood smear and only need a tiny droplet of blood, and so can even be performed at home as part of a self-testing kit. Different tests have been developed to test between the various different species of malaria. While quick and easy, there are some concerns over the sensitivity and specificity of the various tests; trials in the field have gone some way to quantifying the effectiveness of these tests in different contexts. One potential advantage of RDTs is that in some cases they seem capable of positively diagnosing low intensity infections, that would be missed by traditional blood smear. A disadvantage for wide-spread use of these tests, especially in low resource settings, is that they are very expensive.

Finally, the advent of DNA-based techniques for identifying malaria parasites means that PCR (polymerase chain reaction) can be used on a patient’s blood for an almost fool-proof diagnosis, not only of species but also, to a certain extent, of intensity. However, this procedure takes time, is expensive and requires a fully equipped laboratory with trained personnel; as such, it is not usually used for every day diagnosis of malaria infections, and especially not in developing countries where the vast majority of malaria cases occur.

Malaria Blood Work

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QUESTION:

What means smear for malaria – value 1?

ANSWER:

In most cases, I would suggest this means a positive result, though the exact meaning of that depends to some extent to the type of blood test it was. You mention a smear; to me, that implies that the test used traditional microscopy to look for red blood cells infected with malaria parasites. In this case, a result of 1 would indicate that one infected red blood cell was observed, meaning the patient is positive for malaria, although with a light infection (at least at that point in time – especially if the patient had falciparum malaria, the intensity of the infection can increase very rapidly). Otherwise, blood can be used in malaria rapid diagnostic tests (RDTs), which look for antibodies to malaria in the patient’s blood. In this case, the test result can sometimes be denoted by a binary value: in other words, 0 indicates negative and 1 indicates positive.

It is very important to find out from your doctor or clinic exactly what kind of test they ran and what the results mean, to ensure that correct and effective treatment is administered as quickly as possible.