Diagnosing malaria
Clinical diagnosis
Clinical diagnosis is the most widely used approach. It has been the only feasible one in many situations, particularly in rural areas and at the periphery of the health care system where laboratory support to clinical diagnosis does not exist. Among the many clinical signs and symptoms associated with malaria, the most prominent is fever, which is often accompanied by chills, perspiration, anorexia, headaches, vomiting and malaise. Residents of endemic areas are often familiar with this combination of symptoms, and frequently self-diagnose malaria based on symptoms alone. In addition to these symptoms of uncomplicated malaria, other manifestations may develop that signal severe malaria, which is almost always due to Plasmodium falciparum. These include confusion or drowsiness with prostration together with severe manifestations such as cerebral malaria, severe anaemia and others.
Clinical diagnosis is inexpensive to perform, and requires no special equipment or supplies. However, the symptoms of malaria are very non-specific and overlap with those of other febrile illnesses. A diagnosis of malaria based on clinical grounds alone is therefore unreliable, and when possible should be confirmed by laboratory tests.
Clinical manifestations that aid in early diagnosis
Symptoms
Patients present with a variety of symptoms depending on the stage of infection and the infecting species:
- Fever is virtually always present, and fever plus any other symptom might be malaria if there has been exposure to the disease.
- Common complaints include mild to moderate malaise, fatigue, muscle aches, back pain, headache, dizziness, loss of appetite, nausea, vomiting, abdominal pain, and diarrhoea. Some patients report a dry cough and shortness of breath.
- Gastrointestinal complaints can be considerable, suggesting a diagnosis of gastroenteritis.
Young children and semi-immune individuals may complain of fever and headache as their only symptoms
Signs
- Physical examination usually demonstrates an increased temperature, tachycardia, and warm flushed skin.
- The spleen is often palpable in initial infection, but this is more likely in subsequent attacks. It is usually soft, and may be tender.
- The liver is often enlarged and may be tender; jaundice is not unusual.
- Orthostatic hypotension often occurs during initial infections.
Mental confusion and cyanosis are sometimes encountered.
Malaria Clinical Findings
| Sign or symptom | % with finding |
| Fever and chills | 96 |
| Headache | 79 |
| Muscle pain | 60 |
| Palpable liver | 33 |
| Palpable spleen | 28 |
| Nausea and vomiting | 23 |
| Abdominal cramps/diarrhoea | 6 |
Malaria Laboratory Findings
| Finding | Normal range | % with Abnormal findings |
| Reticulocytosis | 3-18% | 42 |
| Thrombocytopenia | 12K-150K | 36 |
| Bilirubin increased | 1-1.8 | 33 |
| VDRL positive | (-) | 28 (+) |
| Anaemia | 5.8-12(Hgb) | 28 |
| Leukopenia | 3000-4700 | 26 |
| Alk. Phos increased | 11-27 | 17 |
| SGOT increased | 40-108 | 10 |
Fever in malaria
The malaria paroxysm is the classical, defining clinical feature of the disease. However, these paroxysms are often not present. Chills or rigor, followed by high fever (40°C or higher) occur in a cyclical pattern in infections due to P. vivax, P. ovale, and P. malariae, but not P. falciparum, which is more likely to show continuous fever with intermittent temperature spikes.
