|Basic Malaria Microscopy (part I and II) (WHO - OMS, 1991, 72 p.)|
By the end of this Unit you should:
· know that blood contaminants
may be confused with malaria parasites
By this stage in your training you are likely to have seen a number of objects in blood films that have caused you some confusion; if you could not identify them as parasites you have probably wondered what they are.
Blood films may contain many features that can cause confusion and problems in diagnosis. Such features are known as artefacts. Some are more common than others; some are easier to prevent than others.
Fungus will show up as artefacts on blood films. The best way to prevent fungal growths on slides is to stain blood films as soon as possible after making and drying them - within 48 hours at most. Unfortunately, this is not always practicable.
Other contaminants will be picked up from the environment. Dust particles floating in the air will settle on blood films while they are drying, either before or after staining. Specks of dirt may be transferred from a patients finger when a blood sample is taken, or the original slide may not be perfectly clean.
Plate 3 shows a variety of artefacts that may be seen in both thick and thin blood films. The examples are not exhaustive but give a good idea of the size, shape and colour of different kinds of artefact.
You may occasionally see microfilariae (e.g. Wuchereria bancrofti) in blood films you are examining. These are not, strictly speaking, artefacts and you should report what you see, both on your record form and directly to your supervisor.