102 PCR Testing for Microorganism Detection: Yea or Nay?

• Published in: American journal of clinical pathology 2018-01, Vol.149 (suppl_1), p.S44-S44
• Main Authors: Graham, Tiffany, Pavlidakey, Peter
• Format: Article
• Language: English
• Subjects: Inflammation; Microorganisms; Pathology; Polymerase chain reaction; Speciation; Tuberculosis
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqx118.101

Abstract Background There is an ever-increasing demand for pathologists to minimize unnecessary testing while performing requests for complex molecular studies. Understanding the efficacy of a test and its role in guiding clinical practice decisions is essential. Herein, we analyze the utility of polymerase chain reaction (PCR) testing for speciation of microorganisms. Methods We retrospectively reviewed our pathology database for cases from 2015 to 2017 with PCR tests requesting bacterial sequencing, fungal sequencing, or the detection of AFB be performed. The type, number, and final result of the PCR tests were determined. Positive cases were further examined for pathologic findings. Results Thirty cases were sent for PCR analysis with an average of 2.9 tests ordered per case. A total of 88 tests were performed, aimed at the detection of mycobacterium tuberculosis (TB) (23/88; 26.1%), non-TB mycobacterium (21/88; 23.9%), bacteria (20/88; 22.7%), fungal organisms (17/88; 19.3%) or “other” (7/88; 8.0%). A positive test result was identified in four cases (4/30 [13.3%]; 4/88 [4.5%]), which included 2/21 (9.5%) non-TB mycobacterium tests, 1/17 (5.9%) fungal tests, and 1/23 (4.3%) mycobacterium TB tests, for an overall positivity rate of 2.3%, 1.1%, and 1.1%, respectively. Of those cases with a positive result, an average of 2.5 tests were ordered, for an average positivity rate of 43.8% per case, or 2.8% overall. All cases displayed a dense inflammatory reaction pattern +/– granulomas and microorganisms were appreciated in three of four (75%) cases via special stains. Conclusion The utilization of routine H&E, special stains, and microbiology cultures are sufficient to guide the clinical management of a patient with suspected infection. PCR testing can provide additional information; however, it is best left to the discretion of the clinician, as he or she can determine if it will adequately change management, given the low yield.