Examination of peripheral blood smear (PBS) is the gold standard for the diagnosis of malaria; however, its diagnostic utility will be dependent on the examiner's microscopic experience, the quality of the smear, and the degree of parasitemia. Therefore, it is essential to have available a rapid and simple test that is as sensitive and specific as PBS, at a small-middle range medical center, a health care center, and a military hospital in a malaria endemic area.
Malaria antigen and antibody tests were performed on 120 febrile patients who were requested for complete blood count (CBC) and PBS at two military hospitals from May 2004 to August 2005.
Of the 45 patients who were diagnosed with malaria by examination of peripheral blood smears, 42 were positive on both malaria antigen and antibody tests, and 2 were positive on either antigen or antibody test. Only 1 patient was negative on the both test. Furthermore, all 75 patients with negative microscopic examinations also had negative malaria antigen and antibody tests.
The results of this study show that a rapid differential diagnosis of malaria can be made by performing malaria antigen and antibody tests on febrile patients at hospitals in malaria endemic areas. Moreover, the test is simple and convenient enough to be performed without any special equipment or experience.
The comparison of results between microscopic exam and rapid diagnostic kits for malaria antigen and antibody test among 120 febrile patients
| Result | Malaria (+) group (n=45) |
Malaria (−) group (n=75) |
||||
|---|---|---|---|---|---|---|
| Microscopy | Malaria Ag test | Malaria Ab test | Microscopy | Malaria Ag test | Malaria Ab test | |
| Positive (+) | 45 | 43 | 43 | 0 | 0 | 0 |
| Negative (–) | 0 | 2 | 2 | 75 | 75 | 75 |
| Sensitivity (%) | 100 | 95.6 | 95.6 | − | − | − |
| Specificity (%) | − | − | − | 100 | 100 | 100 |
The comparison of results between Cho's study[3] and this study according to parasite density
| Group | N of patient | OptiMAL test by Cho's study |
Group | N of patient | SD antigen test by this study |
||||
|---|---|---|---|---|---|---|---|---|---|
| Positive | Negative | Sensitivity | Positive |
Negative | Sensitivity | ||||
| 1 (<100/ |
9 | 5 | 4 | 55.6% | 1a (<50/ |
4 | 3 | 1 | 75% |
| 1b (50–100/ |
4 | 4 | 0 | 100% | |||||
| 2 (−500/ |
9 | 8 | 1 | 88.9% | 2 (−500/ |
12 | 12 | 0 | 100% |
| 3 (−1,000/ |
5 | 4 | 1 | 80.0% | 3 (−1,000/ |
4 | 4 | 0 | 100% |
| 4 (−2,000/ |
8 | 7 | 1 | 87.5% | 4 (−2,000/ |
2 | 2 | 0 | 100% |
| 5 (>2,000/ |
30 | 27 | 3 | 90.0% | 5 (>2,000/ |
19 | 18 | 1 | 94.7% |
| Total | 61 | 51 | 10 | 83.6% | Total | 45 | 43 | 2 | 95.6% |
The results of malaria antigen and antibody tests in this study showed the same results in all of the groups.
The results of malaria antigen and antibody tests comparing with microscopic examination in 10 malaria patients
| Result | Test results at admission |
Follow up test results (After 3–7 days) |
||||
|---|---|---|---|---|---|---|
| Microscopy | Malaria Ag test | Malaria Ab test | Microscopy | Malaria Ag test | Malaria Ab test | |
| Positive | 10 | 10 | 10 | 2 |
2 |
10 |
| Negative | 0 | 0 | 0 | 8 | 8 | 0 |
The parasite density and malaria antigen level were markedly decreased after medication in these malaria patients (less than 100/μL); however, the results of malaria antibody test showed a persistently strong positive pattern.