Diagnostic value of buffy coat preparation in dengue hemorrhagic fever

Examination of the buffy coat preparation is a simple, rapid diagnostic aid for the early diagnosis of dengue hemorrhagic fever (DHF). The presence of many transformed lymphocytes, usually 20-50 per cent during the first few days of fever is a unique finding especially during a secondary infection. Similar findings are absent during the early phase of illness in other viral infections. The buffy coat appearance in DHF is also clearly different from those in patients with bacterial infections, which show many polymorphonuclear leukocytes containing toxic granules and vacuoles. The early buffy coat diagnosis in 320 cases of DHF correlated well with the later serologic diagnosis. The buffy coat diagnosis of secondary DHF was correct in 94.2% of cases as early as the third day of fever. This technique has proven to be clinically useful for early screening test of secondary DHF in Southeast Asian countries. The observation of many transformed lymphocytes in the peripheral blood of DHF patients also offer some insight into the pathogenesis of this condition.