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Pages 73-89

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From page 73...
... 5Diagnostic Tests WHERE WE WANT TO BE IN THE YEAR 2010 There will be the new appreciation of the need for different malaria diagnostics at various levels of the health care system. Malaria assays will be available -- each tailored to a distinct setting -- that will supplement microscopy for diagnosing malaria.
From page 74...
... WHERE WE ARE TODAY The most important role for malaria diagnostics is to help health care workers, whether they be in the village in Mali or in a sophisticated hospital in New York City, select the most appropriate treatment for patients whose illness may be due to infection with malaria parasites. Since the symptoms of malaria vary and can resemble those of other diseases, diagnosing malaria solely on the basis of clinical symptoms is unreliable.
From page 75...
... Microscopy Standard Technique Microscopy is the most widely used laboratory-based diagnostic test for malaria, and it likely will remain the test choice for some time. In this technique, two drops of blood, typically obtained from a finger-pricked by a metal lancet, are placed on a glass microscope slide.
From page 76...
... Quantitative Buffy Coat Technique The quantitative buffy coat (QBC) technique is a commercially available test based on fluorescence microscopy (Wardlaw and Levine, 1983)
From page 77...
... equipment and training would be particularly valuable in field settings. In addition, the medical community's lack of experience in the use of microscopy to diagnose malaria in the United States (and other more developed countries)
From page 78...
... 0.001 percent, equivalent to 50 to 500 parasites per microliter of blood) , with RIA techniques being slightly more sensitive on average.
From page 79...
... addition, competition assays usually require centrifugation to separate red blood cells from autologous serum antibodies that can interfere with the assay and produce false-positive results. This requirement for specimen processing makes performing large numbers of competition assays time-consuming and limits the technique's usefulness in the field.
From page 80...
... sequences which they target are found in abundance in parasite DNA (104 to 105 copies per nucleus)
From page 81...
... possible in less developed settings (Nickerson et al., 1990)
From page 82...
... 1, may indicate acute infection (Früh et al., 1989) ; and antibodies to circumsporozoite proteins as a broad screen for malaria prevalence (Writz et al., 1987)
From page 83...
... researchers, and others contemplating the development of new malaria diagnostics or the improvement of existing tests may find these parameters useful. TABLE 5-1 Suggested Specifications for Malaria Diagnostic Tests Level of Carea Desired Quality of Diagnostic Test 1 2 3 4 5 Identify specimen as positive or negative for malaria + + + + + Identify Plasmodium falciparum + + + + + Identify other human Plasmodium species – + + + + Estimate parasite density – + + + – Use whole blood + + – – – Use small sample volume (no venipuncture)
From page 84...
... TABLE 5-2 Two-by-Two Table for Determining Diagnostic Test Characteristics Disease Status Category Positive Negative Total Test result Positive TP FP TP+FP Negative FN TN FN+TN Total TP+FN FP+TN N Abbreviations: TP, true positive; FP, false positive; FN, false negative; TN, true negative. Formulas for calculating test characteristics: Sensitivity (true-positive rate)
From page 85...
... is still the gold standard of malaria diagnosis. There are circumstances in which new diagnostic techniques would be useful, however.
From page 86...
... Epidemiologists trying to determine the prevalence of malaria infection in a population would benefit from diagnostic tests that are less labor-intensive than standard microscopy. RESEARCH FOCUS: Development of parasite antigen- or nucleic acidbased detection methods that collect finger-prick blood samples for later batch processing and that are inexpensive and easy to perform.
From page 87...
... Fortier, B., P Delplace, J
From page 88...
... 1987b. Use of enzyme-linked synthetic DNA in diagnosis of falciparum malaria.
From page 89...
... 1989. Leishmaniasis and malaria: DNA probes for diagnosis and epidemiologic analysis.

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