Detection of cytomegalovirus DNA in fecal samples in the diagnosis of enterocolitis after allogeneic stem cell transplantation

Performance of Cytomegalovirus Real-Time Polymerase Chain Reaction Assays of Fecal and Plasma Specimens for Diagnosing Cytomegalovirus Colitis

INTRODUCTION

Cytomegalovirus (CMV) viral load detected by real-time polymerase chain reaction (PCR) in plasma or stool may facilitate detection of CMV colitis.

METHODS

This prospective study enrolled 117 patients with clinically suspected CMV colitis. Patients presenting with gastrointestinal symptoms and having increased risk of CMV infection were eligible. All participants underwent colonoscopy with tissue biopsy. Five patients underwent colonoscopy twice because of clinical recurrence, resulting in a total of 122 colonoscopies. Stool CMV-PCR and plasma CMV-PCR were performed within 7 days before/after colonoscopy. Twenty asymptomatic volunteers also underwent the same protocol.

RESULTS

Twenty-seven (23.1%) of 122 colonoscopies yielded positive for CMV colitis. The sensitivity and specificity was 70.4% and 91.6% for stool CMV-PCR and 66.7% and 94.7% for plasma CMV-PCR, respectively. The sensitivity of either positive plasma or positive stool CMV-PCR was 81.5%, which is significantly higher than that of plasma CMV-PCR alone ( P = 0.045). However, positive results from both tests yielded a specificity of 95.8%, which is significantly higher than that of stool CMV-PCR alone ( P = 0.045). There was a good and significant correlation between stool CMV-PCR and plasma CMV-PCR ( r = 0.71, P < 0.01), and both tests significantly correlated with the cytomegalic cell count ( r = 0.62, P < 0.01 for stool and r = 0.64, P < 0.01 for plasma). There were no positive stool or plasma CMV-PCR assays among volunteers.

DISCUSSION

The results of this study strongly suggest that the combination of stool CMV-PCR and plasma CMV-PCR can be used to confidently rule in (both positive) or rule out (both negative) a diagnosis of CMV colitis.

Detection of cytomegalovirus (CMV) by digital PCR in stool samples for the non-invasive diagnosis of CMV gastroenteritis

Background

CMV gastroenteritis is common in patients receiving allogeneic hematopoietic stem cell transplantation and it is difficult to distinguish from acute graft-versus-host disease (aGvHD), which has very similar symptoms but needs quite different treatment. CMV gastroenteritis is caused by local infection or reactivation of CMV in the gastrointestinal tract while aGvHD is due to immune rejection. The gold standard of diagnosis of CMV gastroenteritis and aGvHD is gastrointestinal biopsy under endoscopy, which is invasive and can potentially lead to severe side effects. Stool samples testing with quantitative polymerase chain reaction (qPCR) may be an alternative, while the application in trace level measurements and precision are not all satisfactory enough in reported research.

Methods

In this study, we designed a novel method that extracted the cell free DNA (cfDNA) from the fecal supernatant to perform digital PCR (dPCR) for the detection of CMV, analyzed the performance and compared it with the total DNA extracted by the current procedure.

Results

Twenty-two paired stool samples using two DNA extraction methods proved that the cfDNA extraction method had markedly higher DNA concentrations and control gene copy number, suggesting that cfDNA may be more informative and more useful for the detection of CMV DNA segment. The dPCR approach in detecting CMV DNA segment also exhibit good linearity (R2 = 0.997) and higher sensitivity (limit of detection at 50% was 3.534 copies/μL). Eighty-two stool samples from 44 immunocompromised patients were analyzed, CMV-positive rate was 28%, indicating that more than one-quarter of the gastrointestinal symptoms within these patients may be caused by CMV infection or reactivation.

Conclusion

The combined results suggest that detection of CMV by dPCR in cfDNA of stool supernatant is a powerful method to identify CMV gastroenteritis and helps in clinical treatment decision making.