A child with a history of a pustular rash at the site of a cat scratch on one arm now has warm, tender, swollen axillary lymph nodes on the affected side. The primary care pediatric nurse practitioner notes induration and erythema of these nodes. What will the nurse practitioner do?

A child with a history of a pustular rash at the site of a cat scratch on one arm now has warm, tender, swollen axillary lymph nodes on the affected side. The primary care pediatric nurse practitioner notes induration and erythema of these nodes. What will the nurse practitioner do?

• A. Obtain a complete blood count and C-reactive protein
• B. Order an immunofluorescent assay (IFA) for serum antibodies
• C. Perform a needle aspiration of the affected lymph nodes
• D. Prescribe a 5-day course of azithromycin

Answer: (B)

Regional lymphadenopathy following a cat scratch strongly suggests cat-scratch disease caused by Bartonella henselae. The most informative next step is to obtain serologic evidence of Bartonella infection, typically using an immunofluorescent assay to detect Bartonella antibodies. This test helps confirm the diagnosis noninvasively and distinguishes it from other causes of tender axillary lymphadenopathy, such as bacterial cellulitis, abscess, or other infections. While CBC and CRP can show inflammatory activity, they don’t establish the specific etiology. A needle aspiration would be reserved for a lymph node that is fluctuant or forming an abscess, to drain it and culture the fluid if needed. Starting azithromycin is a treatment option for cat-scratch disease and can shorten the course, but confirming the diagnosis with Bartonella serology guides appropriate management and helps determine whether antibiotics are indicated in this patient. In short, ordering a Bartonella immunofluorescent antibody test is the best step to confirm cat-scratch disease and guide subsequent care.

Regional lymphadenopathy following a cat scratch strongly suggests cat-scratch disease caused by Bartonella henselae. The most informative next step is to obtain serologic evidence of Bartonella infection, typically using an immunofluorescent assay to detect Bartonella antibodies. This test helps confirm the diagnosis noninvasively and distinguishes it from other causes of tender axillary lymphadenopathy, such as bacterial cellulitis, abscess, or other infections.

While CBC and CRP can show inflammatory activity, they don’t establish the specific etiology. A needle aspiration would be reserved for a lymph node that is fluctuant or forming an abscess, to drain it and culture the fluid if needed. Starting azithromycin is a treatment option for cat-scratch disease and can shorten the course, but confirming the diagnosis with Bartonella serology guides appropriate management and helps determine whether antibiotics are indicated in this patient.

In short, ordering a Bartonella immunofluorescent antibody test is the best step to confirm cat-scratch disease and guide subsequent care.