Bronchoalveolar Fluid Viral Load Valuable in Assessing CMV Pneumonia in Immunocompromised Patients

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Identifying optimal bronchoalveolar fluid CMV viral load threshold holds potential for diagnosing CMV pneumonia in immunocompromised patients.
Identifying optimal bronchoalveolar fluid CMV viral load threshold holds potential for diagnosing CMV pneumonia in immunocompromised patients.

NEW ORLEANS – Considering the risks associated with lung biopsy, the diagnosis of cytomegalovirus (CMV) pneumonia—particularly in immunocompromised patients—presents a clinical challenge. However, according to research presented at IDWeek 2016, a CMV viral load of 32,000 IU/mL in bronchoalveolar fluid (BALF) was found to be suggestive of CMV pneumonia in a group comprising mostly lung transplant recipients, a group at high risk for morbidity and mortality from this infection.

From 2000 to 2014, researchers from the Mayo Clinic in Rochester, Minnesota, collected BALF from 40 immunocompromised adults and quantified their CMV viral load using the Cobas® AmpliPrep/Cobas TaqMan CMV Test (Roche Molecular Systems, Inc.).  The World Health Organization's standard for CMV DNA was used for calibrating BALF. Patients who were identified as having CMV following lung biopsy were compared with a control group consisting of patients who underwent collection of BALF for noninfectious causes and whose lung biopsy specimens were negative for CMV.

Forty BALF specimens were tested; 17 were positive for CMV pneumonia (6 proven by biopsy) and 23 were in the control group (2 cases with CMV viral shedding).  The majority of the patients (75%) were lung transplant recipients (71% with CMV pneumonia and 83% in the control group).

“Among the controls, the median viral load was 0 (range, 0-7640 IU/mL), while among CMV pneumonia cases proven by biopsy, the median was 656,000 IU/mL (range, 274-8,200,000 IU/mL)” with a sensitivity and specificity of 100%, the researchers noted.

Among the 17 patients with CMV pneumonia, a “viral load of 32,400 IU/mL in BALF had an 82% sensitivity and 100% specificity for possible, probable, or proven CMV pneumonia,” suggesting that a CMV viral load >32,000 IU/mL in BALF is indicative of CMV pneumonia in immunocompromised patients.

Because of the small cohort involved in this study, the researchers noted that larger, prospective studies should be undertaken to both validate their findings and to identify the optimal BALF viral load threshold in this patient population.

Reference

Beam E, Germer J, Lahr B, et al. Cytomegalovirus (CMV) DNA quantification in bronchoalveolar lavage fluid collected from immunocompromised patients with CMV pneumonia. Presented at: IDWeek 2016. New Orleans, LA; October 26-30, 2016. Abstract 83.

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