Atypical pneumonia testing in transplant recipients

Area of Science:

• Infectious Diseases
• Transplant Medicine
• Clinical Diagnostics

Background:

• Atypical pneumonia diagnosis is challenging in immunocompromised patients.
• The incidence and diagnostic yield of atypical pneumonia in transplant recipients are not well understood.
• This study investigates atypical pneumonia in solid organ, hematopoietic stem cell transplant (HSCT), and CAR T-cell recipients.

Purpose of the Study:

• To assess the test positivity rate of atypical pneumonia in transplant recipients.
• To evaluate the incidence of specific atypical pathogens (Legionella, Mycoplasma, Chlamydia, Bordetella) in this population.
• To analyze the cost-effectiveness of diagnostic testing for atypical pneumonia.

Main Methods:

• Retrospective cohort study at Yale New Haven Health System (January 2016 - August 2022).
• Included adults with solid organ transplant, HSCT, or CAR T-cell therapy who underwent atypical pneumonia pathogen testing.
• Positive results were adjudicated clinically; a cost analysis was performed.

Main Results:

• 1021 tests were performed on 481 transplant recipients, with a 0.7% positivity rate (7 positive tests).
• Three cases of proven Legionella and one possible Mycoplasma infection were identified after adjudication.
• Legionellosis cases occurred within 1 year post-transplant with augmented immunosuppression and lymphopenia.

Conclusions:

• The positivity rate for atypical pneumonia testing in transplant recipients is very low.
• An algorithmic approach to testing, considering clinical factors, may enhance diagnostic yield.
• Targeted testing strategies could lead to significant cost savings in this patient population.