Clinical characteristics, outcome and prognosis of patients with indeterminate Clostridioides difficile results: A retrospective study at SQUH.

Background

Clostridioides diffcile infection (CDI) is a major cause of morbidity and mortality in hospitalized patients. The diagnosis of CDI is challenging with variations in the performance of laboratory tests .The clinical significance of indeterminate C. difficile EIA results (GDH positive toxin negative) needs to be evaluated.

Methods

A retrospective study that was conducted at SQUH from January 2018 to December 2023. Laboratory data of stool samples collected for C. difficile testing was retrieved via the laboratory information system. The clinical charts of patients with indeterminate results were reviewed for demographic characteristics, comorbidities, appropriate indication for C. difficile testing (>=3 loose stool in <= 24 hours, not on laxatives, age >= one year, not tested positive for C. difficile within 14 days), CDI severity, management & patients outcomes during admission, at three months and one year. Findings were compared to antigen positive toxin-positive CDI cases at same period.

Results

The prevalence of C. difficile indeterminate results was 9.317%. Most patients had haemato-oncological comorbidities. Out of 234 patients with indeterminate results, 137 met appropriate testing criteria. Among appropriately tested patients 46 % were treated. For those inappropriately tested, 27.6% were treated despite lacking indications. When comparing C. difficile antigen positive toxin positive patients with C. difficile indeterminate results (n=87 for each), toxin positive patients demonstrated significant high rate of severity (31.4% vs. 12.6%) and fulminant form (3.5% vs. 0) respectively. Toxin positive patients also exhibited worse outcomes during admission, at three months, one years & higher rates of recurrence compared to toxin negative patients.  

Conclusion

This study demonstrates a high prevalence of C. difficile indeterminate results . A proportion of tests were performed in patients who did not meet the clinical criteria for C. difficile testing, resulting in over testing and unnecessary treatment of those patients C. difficile complications. recurrence & severity occur predominantly in Antigen Positive/Toxin Positive patients, while Indeterminate cases usually show milder or colonization-like behavior .These findings emphasize the need for clinical correlation combined with diagnostic stewardship & a two-step algorithm approach to optimize the accuracy of testing results thus improve clinical outcome.

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