Screening for Humoral Immunodeficiency in Patients with Community-Acquired Pneumonia.

ABSTRACT

BACKGROUND: Immunodeficiency is an underrecognized risk factor for infections, such as community-acquired pneumonia (CAP). OBJECTIVE: We evaluated patients admitted with CAP for humoral immunodeficiency. DESIGN: Prospective Cohort Study. SETTING: Inpatients. PATIENTS, INTERVENTION, AND MEASUREMENTS We enrolled 100 consecutive patients admitted with a diagnosis of CAP from February 2017 to April 2017. Serum IgG, IgM, IgA, and IgE levels were obtained within the first 24 hours of admission. CURB-65 score and length of hospital stay were calculated. The Wilcoxon rank-sum test, Kruskal-Wallis test, and simple linear regression analysis were used in data analysis. RESULTS: The prevalence of hypogammaglobinemia in patients with CAP was 38% (95% confidence interval 28.47% to 48.25%). Twenty-seven of 100 patients had IgG hypogammaglobinemia (median 598 mg/dL, IQ range 459-654), 23 of 100 had IgM hypogammaglobinemia (median 38 mg/dL, IQ range 25-43), and 6 of 100 had IgA hypogammaglobinemia (median 36 mg/dL, IQ range 18-50). The median hospital length of stay for patients with IgG hypogammaglobinemia was significantly higher when compared to patients with normal IgG levels (five days, IQ range [3-10] vs three days, IQ range [2-5], P = .0085). Fourteen patients underwent further immune evaluation, resulting in one diagnosis of multiple myeloma, three patients diagnosed with specific antibody deficiency, and one patient diagnosed with selective IgA deficiency. CONCLUSION: There is a high prevalence of hypogammaglobinemia in patients hospitalized with CAP, with IgG and IgM being the most commonly affected classes. IgG hypogammaglobinemia was associated with an increased length of hospitalization. Screening immunoglobulin levels in CAP patients may also uncover underlying humoral immunodeficiency or immunoproliferative disorders.