Rocky Mountain spotted fever physical examination

Physician diagnosis
There are several aspects of RMSF that make it challenging for healthcare providers to diagnose and treat. The symptoms of RMSF vary from patient to patient and can easily resemble other, more common diseases. Treatment for this disease is most effective at preventing death if started in the first five days of symptoms. Diagnostic tests for this disease, especially tests based on the detection of antibodies, will frequently appear negative in the first 7-10 days of illness. Due to the complexities of this disease and the limitations of currently available diagnostic tests, there is no test available at this time that can provide a conclusive result in time to make important decisions about treatment.

For this reason, healthcare providers must use their judgment to treat patients based on clinical suspicion alone. Healthcare providers may find important information in the patient’s history and physical examination that may aid clinical suspicion. Information such as recent tick bites, exposure to high grass and tick-infested areas, contact with dogs, similar illnesses in family members or pets, or history of recent travel to areas of high incidence can be helpful in making the diagnosis. Also, information about the presence of symptoms such as fever and rash may be helpful. The healthcare provider may also look at routine blood tests, such as a complete blood cell count or a chemistry panel. Clues such as a low platelet count (thrombocytopenia), low sodium levels (hyponatremia), or elevated liver enzyme levels are often helpful predictors of RMSF but may not be present in all patients. After a suspect diagnosis is made on clinical suspicion and treatment has begun, specialized laboratory testing should be used to confirm the diagnosis of RMSF.

The diagnosis of RMSF must be made based on clinical signs and symptoms, and can later be confirmed using specialized confirmatory laboratory tests. Treatment should never be delayed pending the receipt of laboratory test results, or be withheld on the basis of an initial negative finding for R. rickettsii.

Rash
While most people with RMSF (90%) have some type of rash during the course of illness, some people do not develop the rash until late in the disease process, after treatment should have already begun. Approximately 10% of RMSF patients never develop a rash. It is important for physicians to consider RMSF if other signs and symptoms support a diagnosis, even if a rash is not present.

A classic case of RMSF involves a rash that first appears 2-5 days after the onset of fever as small, flat, pink, non-itchy spots (macules) on the wrists, forearms, and ankles and spreads to include the trunk and sometimes the palms and soles. Often the rash varies from this description and people who fail to develop a rash, or develop an atypical rash, are at increased risk of being misdiagnosed.

The red to purple, spotted (petechial) rash of RMSF is usually not seen until the sixth day or later after onset of symptoms and occurs in 35-60% of patients with the infection. This is a sign of progression to severe disease, and every attempt should be made to begin treatment before petechiae develop.