Apparatus for Concentrating Parasitized Red Cells for Testing

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The laboratory diagnosis of malaria has changed little in over 100 years. A finger stick is made and a smear on a glass slide is made and stained and a technologist then uses a microscope to scan over the whole smear which may take up to 15 minutes. A report of "none seen" is widely accepted by doctors as a NEGATIVE. Newly infected individuals may have nearly all of their parasitized red cells hung up (sequestrated) in their micro circulation and a "none seen" report may lead the doctor to diagnose the patient with flu or a bacterial infection which is a dangerous diagnosis as it delays treatment, sometimes fatally.

It has been discovered that malaria parasites in red cells eat hemoglobin and store the iron in a vacuole. This concentrated stored iron is enough to make the red cell magnetic.

My apparatus consists of a strong neodymium iron boron magnet in a base with a vertical tube above this base. This apparatus is designed to receive a conical centrifuge tube. For malaria testing the tube is filled with saline and blood is added and suspended in the solution. Then the tube is placed over the magnet for 2 minutes and the magnetic field will pull the parasitized red cells to the bottom of the tube to form a "button." This is like finding all the needles in a hay stack by using a strong magnet. The tube is decanted using a hand magnet and the button is then re-suspended and placed on a slide for staining and reading. 15 ML conical centrifuge tubes are common in the medical lab, and also larger conical tubes. Several drops of blood can be tested using this concentration means. The concentration is perhaps 100 or 200 X over the old blood film method and the "hunting" time is greatly reduced. Confidence in test results will be greatly increased.

For testing and demonstration and teaching I have suspended black photo copier toner in a 15 ml conical test tube filled with water and placed it over the magnet and in just a minute a black button forms, but not until it is placed over the magnet.

The magnets cost is about $7.00 US and the base and tube can be cheaply constructed from plastic. There are cautions for strong magnets. Conical tubes can be reused as lab wear.

There are about 1200 cases of malaria each year from travelers returning to the USA and about 100 of these are fatal from missed diagnoses and confusion over "none seen."

In the third world malaria testing needs this improvement which is inexpensive, accurate, easy, and provides quicker results.

This apparatus can also be used with a new vital staining technique and a water immersion microscope lens for very fast and accurate malaria diagnostic testing.


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  • Name:
    Robert Yancey
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    I have been interested in improving the medical diagnosis of malaria since i worked for a few years in a medical laboratory in a developing country. I was surprised to read one day that parasitized red cells were magnetic. One person had proposed a way to measure the parasitemia by making measurements of opacity of a suspension of blood in saline before and then after a magnetic field was applied to a cuvette. But in most cases the parasitemia is too low to detect in this way. So after thinking about this new concept that red cells become magnetic when parasitized with malaria plasmodia i decided to use a magnetic field to concentrate the parasitized red cells into one spot for observation (microscopy). This would be most valuable. Sometimes finding one parasitized red cell is like finding a needle in a hay stack - but using a strong magnet might not be so bad. After several experimental apparatus i finally made an inexpensive, reusable, and easy to use device.
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