Dr. Sushil Shah and Dr. Nilesh Shah from Metropolis Health Services Pvt. Ltd.,
Mumbai, on page 284, report a very exciting finding of cross reactivity when
testing blood samples of fever patients for dengue viral fever and leptospirosis.
In the last issue of Bombay Hospital Journal, I drew the attention of the Family
Physicians to start asking for indirect blood tests to diagnose the above two
illnesses.1 Now that Sushil Shah and Nilesh Shah have drawn our attention to
the above finding, which is reported perhaps for the first time in world literature,
it will be advisable for our readers to read my article in detail.
1 First of all, a clinical diagnosis is very important. These illnesses should
be suspected in any patient, who suddenly becomes very sick and ill with very
high fever in first 24 hours only. Complaints of skeletal pains specially in
the back, all the bones and joints and even eye balls (in the past, dengue fever
was known as break bone fever), appearance of rash or lymphadenopathy, will
help in the diagnosis of dengue fever. Severe muscle pains especially in calf
muscles and injected bulbar conjunctiva of the eyes (though this finding and
pain on rotating the eyeballs could also be present in dengue) would favour
the diagnosis of leptospirosis.
Talking about the investigations, a simple leucocyte count will, more or less
in all cases, differentiate between these two illnesses. In dengue viral fever,
leucocyte count is markedly low, while in leptospirosis, it is not only high
but markedly high and may go upto 50,000. A routine urine examination of dengue
is normal, while in leptospirosis, it is always abnormal and may show presence
of albumin, casts, RBC and bile pigments.
Instead of asking for a CBC test, it is always better to send the blood to the
laboratory which is doing haemograms where the platelet count is always reported
(and as in falciparum malaria, so in case of dengue fever, the platelet count
is very low). In fact, repeating the platelet count in dengue fever can predict
the haemorrhagic variety of dengue fever, and the patient can be sent to ICU
and the life of the patient can be saved. Similarly asking for a battery of
tests like the SMA 12 is often very helpful because the combination of abnormality
in the liver function tests and the kidney function tests like increased SGPT,
bilirubin, blood urea and creatinine is diagnostic of leptospirosis and any
antibiotic, from penicillin or tetracycline group or doxycycline can cure the
Yes, the Elisa tests for IgM antibodies for both are extremely useful, but more
for excluding the illnesses. Now that the cross reactivity has been
shown, the family physicians will have to diagnose the two illnesses by history
taking and clinical examination (red eyes and marked tenderness of calves).
A routine haemogram rather than CBC, urine examination and SMA 12, should be
asked for, instead of asking for only Elisa test for IgM antibodies, which could
1. Kapoor OP. Why not to start indirect blood testing to diagnose malaria, typhoid,
dengue and leptospirosis. Bombay Hospital Journal 2003; 1 : 134.