[315] High Correlation between Molecular Sequencing and Histopathological Examination of Parallel Samples in Culture-Negative Endocarditis

Angela MB Collie, Nabin K Shrestha, Geraldine S Hall, E Rene Rodriguez, Carmela D Tan. Cleveland Clinic, Cleveland, OH

Background: Microbiological cultures of blood and excised valves are often negative in patients undergoing surgical interventions. Thus, molecular sequencing of cardiac valve specimens is increasingly used to identify the specific organism(s) involved in culture-negative endocarditis. The present study examines molecular sequencing and histopathological results on parallel cardiac valve specimens and identifies histopathologic features common to positive specimens.
Design: All cardiac valve specimens with molecular PCR sequencing results were identified at our institution. For cases where a surgical specimen was available, the histologic features of acute inflammation, necrosis, chronic inflammation, granulation tissue, and fibrinous vegetations were analyzed. Organisms were identified with special stains including Gram, Gomori methenamine silver, and periodic acid-Schiff. PCR sequencing results, including bacterial 16S rRNA, acid fast bacterial heat shock protein 65, and fungal 28S rRNA, were obtained. Molecular results and histopathologic characteristics were compared.
Results: One hundred eleven cardiac valves from 100 patients had PCR results and histologic examination of a parallel surgical specimen. Seventy eight valves (70%) had agreement in the presence or absence of organisms in both studies (Table 1). Three valves (3%) had organisms identified histologically that were not identified by PCR. Thirty valves (27%) did not have an organism identified histologically but did have an organism identified by PCR. When organisms were not identified histologically, acute inflammation was more common in valves with positive PCR (50%) compared with negative PCR (25%) (p<0.001), and fibrinous vegetations were more common in valves with positive PCR (23%) compared with negative PCR (9%) (p<0.01). Necrosis was only observed in PCR positive cases.

Table 1. PCR Results and Histological Examination in 111 Cardiac Valves

Histological examination (diagnosis)	PCR positive	PCR negative
Organisms identified	44	3
Organisms not identified	30	34

Conclusions: Molecular sequencing of cardiac valve samples in culture-negative endocarditis is valuable in diagnosis. The current study could be complicated by sampling error, in that parallel rather than exact specimens were analyzed. However, there is high correlation between PCR sequencing and histological examination. Both studies provide complementary and valuable results.
Category: Cardiovascular

Tuesday, March 20, 2012 2:00 PM

Platform Session: Section H2, Tuesday Afternoon