Rationale:

• Certain physical exam findings, such as a blotchy skin rash, are characteristic of dengue. The skin rash may only first appear later in the illness (e.g., during convalescence). Other features may suggest an alternate diagnosis; for example, deeply icteric injected conjunctiva with hemorrhage suggests leptospirosis.

Evidence:

• A prospective evaluation of the standard sphygmomanometer cuff tourniquet test compared with a simple elastic cuff tourniquet test was conducted in 1136 children with suspected dengue infection admitted to a provincial pediatric hospital in southern Vietnam. Positive results were found in only 42% of children infected with the dengue virus (58).
• Investigators collected data on dengue in international travelers from 14 European clinical referral centers within the European Network on Surveillance of Imported Infectious Diseases between 2003 and 2005. As in the Vietnamese study, the sensitivity of the tourniquet test among this group of travelers was relatively low (44%) (50).
• Surveillance data from Puerto Rico for 1990 and 1991 identified 3926 patients with laboratory-confirmed dengue, including 889 for whom dengue immunologic status and symptoms could be ascertained. A typical macular or maculopapular rash that is often confluent with sparing of small islands of normal skin was seen in approximately 50% of the patients (59).
• The WHO has established case definitions for dengue fever, dengue hemorrhagic fever, and dengue shock syndrome (55).

Comments:

• The tourniquet test for capillary fragility is done by inflating a blood pressure cuff on the upper arm to a point midway between systolic and diastolic blood pressures for 5 minutes.
• The test result is considered positive if 20 or more petechiae appear in a square-inch (6.25-cm²) patch on the forearm after deflation of the blood pressure cuff.