As lukasz frackowski explains, the thick smear is used to make the diagnosis of malaria as it is a concentration technique. In an attempt to explain the shortcomings of the routine thickfilm examination in the diagnosis of scanty malaria parasitaemias, a direct comparison, in terms of positivity and parasite counts, was made between the results of routine thickfilm study and longterm examination of thin films taken at the same time from the same individuals. Peripheral smear study for malarial parasites the mp test. For rapid diagnosis, make thick and thin smears on separate slides. A combined algorithm for malaria detection from thicksmear. The definitive diagnosis of malaria infection is still based on finding malaria parasites in blood films. However, malaria parasites may be missed on a thin blood film when there is a low parasitaemia. Microscopy of thick blood films is the usual diagnostic test for plasmodium falciparum malaria. The blood film method for the laboratory diagnosis of malaria remains the gold standard. A thick blood smear is a drop of blood on a glass slide. Its diagnostic accuracy is adversely impacted by interintraobserver variability, particularly in large. Pdf thick blood films are routinely used to diagnose plasmodium.
A lab technician, doctor, or nurse will take some of your blood and send it to a lab to be stained to make any. The thick blood smears are prepared for detecting the blood parasites such as plasmodium spp. Thick and thin blood smears for malaria michigan medicine. Basic malaria united states centers for disease control. Pdf thick blood film examination for plasmodium falciparum. Doctors use thick and thin blood smears to determine whether you have malaria.
With a thick blood film, the red cells are approximately 6 20 layers thick which results in a larger volume of blood being examined. For optimal clinical management of malaria patients, speciesspecific diagnosis is required. Thick smears are made by dropping 10 to 20 l of blood onto a slide and spreading it into a dimesized area with a glass, wooden, or plastic applicator. The probability of detecting a malaria infection is a function of the amount of blood examined. Staining of the thick thin smear with giemsa stain. The thick blood films are used for microscopic detection of plasmodium parasites, the causal agent of malaria, or for detection of other blood parasites trypanosoma sp. A positive blood smear that is misread as negative. This procedure describes the preparation of thick blood films. Often there are few parasites in the blood at the time the test is done. Malaria worlds second biggest killer plasmodium spp. Modified method for dehemoglobinization of thick smear for malaria diagnosis doi. In preparations from normal patients, the thin section of the smear occupies approximately of the total area and, within that area.
Procedure for thick blood film staining technique a thick film was made by placing a large drop of blood about 15mm in size on the centre of greasefree microscopic slide. For example, they are often not adequate for species identification of malaria parasites. Update on malaria diagnostics and test utilization. Thin and thick blood smears should be prepared immediately or within 1 hour after collection. Malaria was diagnosed when a child presented with fever and a positive blood smear. So a thin smear has to be subsequently examined to identify the species. Thus, thick smears allow a more efficient detection of parasites increased sensitivity. Thin smears are made as per routine hematology differentials. Laboratory diagnosis of malaria learn microbiology online.
Preparation of thick blood films and giemsa staining. These are the most common and accurate malaria tests. Thin films are similar to usual blood films and allow species identification because the parasites appearance is best preserved in this preparation. If thick films are positive, the species should be.
If one test is negative and no parasites are found, you will have repeated blood. Remove thin smear slides and rinse by dipping 34 times in the giemsa buffer. Routine use of thick and thin films is advised for malaria diagnosis. Video tutorial on how to perform a proper thick and thin smear for malaria diagnosis by stephane proux, malaria diagnosis lab supervisor at. Thick films are more difficult to interpret but greatly increase sensitivity by concentrating cells and organisms. Useful for diagnosis of malaria, ehrlichia, trypanosomiasis or microfilariasis, parasitic. Labeling of the slides a write the lab number on the frosted area of the slide using a omnichrom pencil b counter check the lab number on the slide with that on the. Question when malaria is dormant in the body can it be detected in a blood test. The thin end of the film becomes thinner gradually and does not have grainy streaks, troughs, ridges, waves or holes features that can result in an uneven distribution of leukocytes. Microscopy is known to be sensitive and specific but this technique is highly dependent on the skills of microscopists.
Thin blood films have a low sensitivity for detection of malaria parasites. Preparation of thick blood films and giemsa staining lqm. Patients with a relapse case or an early primary case may also few organisms in the blood smear. Thick blood smears are most useful for detecting the presence of parasites, because they examine a larger sample of blood. A combined algorithm for malaria detection from thick smear blood slides kaushik chakrabortya, arnab chattopadhyayb, amlan chakrabarti, tinku acharyad and anjan kr dasguptae department of biochemistry and center for excellence in systems biology and biomedical engineering, university of calcutta, kolkata 700019, india journal of j o u r n a l. Modified method for dehemoglobinization of thick smear for. Using the corner of a clean slide, spread the drop of blood in a circle the size of a dime diameter 12 cm.
Detection of circulating malariaspecific antigens using rapid diagnostic test rdt, or detection of species specific parasite dna in a sample of peripheral blood using a clia validated polymerase chain reaction test pcr, or detection of malaria parasites in thick or thin peripheral blood films with report of percent parasitemia. Fields stain is a histological method for staining of blood smears. Differences between thick blood smear and thin blood smear. The thin blood smear is prepared for studying the morphology of the blood cells and for the identification of microbial agents. The most economic, preferred, and reliable diagnosis of malaria is microscopic examination of blood films because each of the four major parasite species has distinguishing characteristics. A comparative study of thick and thin blood films in the diagnosis. What are the advantages of thin blood smear and thick. The thin smear keeps the red blood cells intact and as moses ngeiywa. Realtime malaria parasite screening in thick blood smears. Microscopic examination of blood smears has been the gold standard for malaria. Thick films should be examined by two observers, each viewing a minimum of 200 high power fields. Visual criteria are used to detect malaria parasites and to differentiate when possible the various species. Thick smears require considerable experience with malaria, as they increase the number of cells examined in a given time period by a factor of about 12. Learners guide isbn 978 92 4 154782 6 microscopists are vital to malaria programmes, and their diagnostic.
In thin films the red blood cells are fixed so the morphology. Malaria test procedure, preparation, principle, results. The definitive diagnosis of malaria infection and other parasites is still based on finding such organisms in blood films. Thick films should be stained using giemsa or field stain.
Prepare a thin and thick smear of the specimen on the same slide which can be done by dividing the slides into two parts and then making the thin smear on one side and thick on the other side. Learners guide second edition basic malaria microscopy part 1. Thick smears should be left in buffer for 5 minutes. Without delay, the blood was spread with a glass spreader held at a steep angle to. Both thick and thin bl films should be examined at length and under oil immersion 100x oil immersion objective. Therefore, examination of a thick blood film is recommended. Malaria test was conducted using the thick and thin film method as described by the.
The incidence of malaria was compared using negative binomial regression controlling for potential confounders with measures of association expressed as an incidence rate ratio irr. While transferring blood with a micropipette to a slide, it is advisable to use reversepipetting to prevent the formation. A thin blood smear, also called a blood film, is one drop of blood spread across most of the slide. Plasmodium falciparum centers for disease control and. Therefore they are used in conjunction with thick blood films, in order to identify the malaria species that was detected by microscopic examination of the thick blood film. Hence, almost all investigations use the thick smear technique.
Difference between thick blood smears and thin blood smears. How to perform a proper thick and thin smear for malaria diagnosis. Manual identification and counting of parasitized cells in microscopic thickthinfilm blood examination remains the common, but burdensome method for disease diagnosis. Thin films should be stained with giemsa stain or leishman stain. What is the difference between thick and thin blood smears. Staining the thin and thick blood smear on the same slide with giemsa stain. Do not make the smear too thick or it will fall off the slide. Light microscopy of thick and thin stained blood smears remains the standard method for. Thick and thin blood smear for malaria diagnosis learn. Malariapositive blood should be used to prepare qc thick and thin films, which are then. Blood specimen collected from the patient is spread as a thick or thin blood smear, stained with a romanovsky stain most often giemsa, and examined with 100x oil immersion objective. Prepared peripheral blood smears, thick and thin, andor whole blood edta samplespecimen type for testing prepared peripheral blood smears, thick and thin, andor edta blood minimum volumesize required 1 ml storagepreservation prior to shipping ambient.
For perfect malaria staining the ph of the buffer should be 7. Thick blood film examination for plasmodium falciparum. Research open access the association between malnutrition. A normal malaria blood test consists of a thick or thin smear, which is often stained and then looked at under a microscope. How ever, in most early and in some recent works thin. At present, microscopy of giemsastained thick and thin blood smear represents the golden standard in malaria diagnostics. If one test is negative and no parasites are found, you will have repeated blood smea.
Two type of blood smear for detection of malaria parasite a thick film b thin film preparation of thin and thick smear on the same slide. In a thick smear 20 times the amount of blood in a thin smear can be examined in the same time. How to perform a proper thick and thin smear for malaria. Follows this procedure for preparation and staining of thick. Background malaria is a lifethreatening disease caused by plasmodium parasites that infect the red blood cells rbcs. Density is usually assessed by thick films, either by counting parasites per microscope field, or by counting parasites per hundred white blood cells.
A thin blood smear is a drop of blood that is spread across a large area of the slide. Diagnostic performance of rapid diagnostic tests versus. Procedure for thick and thin blood film staining technique. Examination of thick blood films for malaria parasites.