Febrile Antibodies Panel

This panel comprises antibody testing for infections caused by Ricketssia rickettsii, Richetssia typhi, Salmonella, and Brucella in patients with fever. A 4-fold change in titers of antibodies between acute and convalescent sera confirms the infection. This panel provides targeted identification of antibodies, which supports differential diagnosis and can provide evidence of exposure.

R rickettsii causes Rocky Mountain spotted fever (RMSF), the most severe rickettsial disease in the United States. RMSF is transmitted via several species of ticks and occurs most commonly in North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma. Fever and headache along with other nonspecific symptoms begin 3 to 12 days after the bite. Serious complications that affect multiple systems may develop quickly and can lead to death in days, especially in children under 10 years old. Thus, early diagnosis and treatment are critical to survival [1].

R typhi causes flea-borne (murine) typhus. The geographic distribution of murine typhus extends throughout tropical and subtropical areas worldwide; it is rare in the United States, occurring mainly in Southern California, Hawaii, and Texas. Fever begins with chills and can last about 12 days. Severe complications can happen, if the infection is not treated, but are unusual [2].

Salmonella infection can be caused by eating contaminated foods including vegetables, eggs, chicken, pork, and fruits. It can also spread between people and from animals to people. Common symptoms, such as diarrhea, fever, and stomach cramps, are usually self-limiting. However, children under 5 years old, adults over 65, and people with compromised immune systems may develop serious or fatal complications [3]. This panel can detect antibodies to 5 Salmonella antigens: H type A, B, and D; O type Vi and D.

Brucella infections are commonly acquired from farm animals and raw dairy products in countries without effective public health and domestic animal health programs. Fever and other nonspecific symptoms of brucellosis start suddenly and later may become remittent. Recurrent brucellosis affects multiple systems with endocarditis as one of the most severe complications [4].

Clinical false-negative results for IgG- and IgM-based serologic tests can occur due to compromised immunity, testing before antibody response has started, or the presence of interfering substances in host serum. A 4-fold change in titers of antibodies between acute and convalescent sera confirms the infection [1,2,4].

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

References
1. Rocky Mountain spotted fever (RMSF). Centers for Disease Control and Prevention. Accessed September 25, 2021. https://www.cdc.gov/rmsf/index.html
2. Flea-borne (murine) typhus. Centers for Disease Control and Prevention. Accessed September 25, 2021. https://www.cdc.gov/typhus/murine/index.html
3. Salmonella. Centers for Disease Control and Prevention. Accessed September 25, 2021. https://www.cdc.gov/salmonella/
4. Brucellosis. Centers for Disease Control and Prevention. Accessed September 25, 2021. https://www.cdc.gov/brucellosis/