Detection of BioFire PNplus Panel pathogens by BioFire PNplus and SOC
Of the 2476 specimens tested with BioFire PNplus, 13 specimens (0.53%) gave invalid results (5 SLS; 8 BLS) leaving 2463 specimens (1237 SLS, 1226 BLS) evaluable. BioFire PNplus Panel detected one or more pathogens in 1875 specimens (76.13%) and SOC in 1380 specimens (56.03%) (p ≤ 0.0001) (Fig. 1). In total, 3893 bacteria and viruses were detected by at least one method (Table 1). BioFire PNplus Panel detected 3743/3893 pathogens (96.15%) compared to 1995/3893 pathogens (51.25%) for SOC (p ≤ 0.0001). BioFire PNplus Panel and SOC concordance for all pathogens detected was 47.39%. Sensitivities of BioFire PNplus Panel detections ranged from 85.54 to 100%, and sensitivities of SOC detections ranged from 8.89 to 100%.
Table 1 Summary of total, BioFire Pneumonia plus (PNplus) Panel, and standard of care (SOC) detections for all pathogens and for all specimen types
For all specimen types, 3262 bacteria were detected by at least one method (Table 1). BioFire PNplus Panel detected 3125/3262 bacteria (95.77%) and SOC 1861/3262 (57.05%) (p ≤ 0.0001). BioFire PNplus Panel and SOC concordance was 52.85%. The most frequently detected bacteria per sample by BioFire PNplus Panel were S. aureus (21.15%), Haemophilus influenzae (19.69%), and Pseudomonas aeruginosa (15.63%) and by SOC were P. aeruginosa (12.83%), S. aureus (12.71%), and H. influenzae (8.65%).
For BLS, 1358 bacteria were detected by at least one method (Supplemental Table 9). BioFire PNplus Panel identified 1288/1358 bacteria (94.85%) compared to 841/1358 (61.93%) for SOC (p ≤ 0.0001). BioFire PNplus Panel and SOC concordance was 56.77%. For SLS, 1904 bacteria were detected by at least one method (Supplemental Table 10). BioFire PNplus identified 1836/1904 (96.43%) bacteria and SOC 1020/1904 (53.57%) (p ≤ 0.0001). BioFire PNplus Panel and SOC concordance was 50%. PPAs for the individual PNplus common bacterial pathogens ranged from 68.42 to100% (mean 92.90%; 95% confidence interval [CI] 91.61 to 94.04%) for all specimens combined; 50.0 to 100% (mean 91.77%; 95% CI 89.66 to 93.56%) for BLS; and 80.95 to 100% (mean 93.74%; 95% CI 92.03 to 95.18% ) for SLS.
NPAs for the individual BioFire PNplus Panel common bacterial pathogens ranged from 87.07 to 99.31% (mean 96.10%; 95% CI 95.89 to 96.30%) for all specimens combined; 90.18 to 99.43% (mean 97.14%; 95% CI 96.89 to 97.39%) for BLS; and 83.86 to 99.19% (mean 94.98%; 95% CI 94.73 to 95.37%) for SLS. NPVs for the individual BioFire PNplus Panel common bacterial pathogens ranged from 99.04 to 99.96% (mean 99.63%; 95% CI 99.56 to 99.68%) for all specimens combined; 99.0 to 99.92% (mean 99.61%; 95% CI 99.51 to 99.69%) for BLS; and 99.15 to 99.94% (mean 99.64%; 95% CI 99.54 to 99.71%) for SLS. This evaluation did not consider the quantity of the common bacterial pathogens reported and the NPA and NPV may in practice be higher based on laboratory sample type and pathogen reporting thresholds. Overall for specimens negative by BioFire PNplus Panel but positive by SOC culture for which either a semiquantitative or quantitative result was provided, 45.1% had quantities reported by SOC (e.g., 1+, rare, 1 colony, < 103) that would be considered below the level of detection of the BioFire PNplus Panel.
C. pneumoniae, M. pneumoniae, and L. pneumophila were detected in 0.28%, 1.66%, and 2.23% of all specimens, respectively. Sensitivities of C. pneumoniae, M. pneumoniae, and L. pneumophila detections by BioFire PNplus Panel were 100% (7/7), 90.24% (37/41), and 89.09% (49/55) respectively, and SOC were 57.14% (4/7), 48.78% (20/41), and 89.09% (49/55), respectively (Table 1). Detection of M. pneumoniae was significantly better by BioFire PNplus Panel than SOC (p = 0.0001). BioFire PNplus Panel and SOC detection rates for atypical bacteria combined were 90.29% (93/103) and 70.87% (73/103), respectively (p = .0008). BioFire PNplus Panel detected 97.94% (618/631) of the total viral detections and SOC 21.24% (134/631) (p ≤ 0.0001). RV/EV was the predominant virus group detected (58.32%), followed by PIVs (10.78%) and the non-SARS-CoVs (8.24%).
Single and codetections for BioFire PNplus pathogens identified by BioFire PNplus and SOC
Distribution of negative and positive results for all specimens and breakdown of composition for BioFire PNplus Panel and SOC are shown in Figs. 2. and 1. Majority of BioFire PNplus Panel results (70.57%) and SOC results (55.75%) contained at least one bacteria, and at least one virus was detected in 20.49% and 2.93% of specimens, respectively. Mean number of bacteria and viruses detected by BioFire PNplus Panel in all specimens, BLS, and SLS were 1.99, 1.8, and 2.15, respectively, compared to 1.44, 1.44, and 1.8 respectively, by SOC (Table 2). For all specimens, 73.81% of BioFire PNplus Panel positive specimens (n = 1875) contained 1 (45.22%) or 2 (28.59%) pathogens compared to SOC positive specimens (n = 1380) where 92.32% contained 1 (65.51%) or 2 (26.81%) BioFire PNplus Panel pathogens.
Table 2 Number of pathogens (contained in the BioFire PNplus Panel) detected by BioFire Pneumonia plus (PNplus) Panel versus standard of care (SOC)
Among the 1027 BioFire PNplus Panel specimens with codetections, 63.0% (647/1027) had only multiple bacteria (2 to 8); 35.44% (364/1027) had both bacteria (1 to 7) and virus(es) (1 to 3); and 1.33% (16/1207) had only 2 viruses detected. Among the 476 SOC specimens with codetections, 86.34% (411/476) had only multiple bacteria (2 to 5); 13.03% (62/476) had both bacteria (1 to 5) and virus(es) (1 to 2); and 0.63% (3/476) had 3 viruses only detected.
Pathogens detected by SOC not included in BioFire PNplus Panel
Excluding normal oral flora, 649 additional potential pathogens were detected by SOC including 230 gram-negative bacteria, the most prevalent being Stenotrophomonas maltophilia (n = 70), Citrobacter spp. (n = 31), Acinetobacter spp. (n = 28), Haemophilus parainfluenzae (n = 22), Morganella morganii (n = 15), and Hafnia alvei (n = 11). Another 28 gram-negative bacterial spp., representing 18 genera, were reported less than 10 times. Yeasts were reported for 283 specimens, Candida spp. (n = 123), Candida albicans (n = 113), C. glabrata (n = 27), C. parapsilosis (n = 6), C. krusei (n = 5), C. tropicalis (n = 5), C. kefyr (n = 2), and C. lusitaniae (n = 2). Pneumocystis sp. was reported for 11 specimens, molds for 28 specimens, including 11 Aspergillus fumigatus, and five anaerobes including three Fusobacterium spp. There were 42 gram-positive cocci of questionable significance including 24 Enterococcus spp. and seven Streptococcus C/G groups. There were 24 gram-positive rods, including 15 Corynebacterium spp. and 1 Nocardia sp. and four Mycobacterium (two M. tuberculosis, one M. avium, and one M. fortuitum). Additional viral targets (n = 22) included cytomegalovirus (n = 10), herpes simplex virus (n = 5), Epstein-Barr virus (n = 4), human herpes virus 6 (n = 2), and varicella zoster virus (n = 1).
Including BioFire PNplus Panel pathogens and additional SOC pathogens not in BioFire PNplus Panel, the number of potential pathogens for all specimens totaled 4542, of which BioFire PNplus Panel detected 82.41% (3743/4542) and SOC detected 58.21% (2644/4542) (p ≤ 0.0001). Excluding pathogens of questionable significance that may be considered colonizers (yeasts, gram-positive cocci, gram-positive rods [excluding Mycobacteria spp., Nocardia spp.], molds [due to difficulty in interpretation even in immunocompromised persons]), the total number of potential pathogens was 4274 of which BioFire PNplus Panel detected 87.58% (3743/4274) and SOC detected 55.59% (2376/4274) (p ≤ 0.0001). The NPVs for individual pathogens not included in the BioFire PNplus Panel ranged from 97.16% for S. maltophilia to 99.96% for organisms reported only once. The composite NPV of the BioFire PNplus Panel for all off-panel pathogens minus those of questionable significance was 89.12%. This evaluation did not consider the quantity of the off-panel pathogens reported and the NPV may in practice be higher based on laboratory sample type and pathogen reporting thresholds.
Concordance of BioFire PNplus Panel and SOC results
Overall, 1209/2463 specimens (49.10%) demonstrated total concordance between BioFire PNplus Panel and SOC results (Table 3). This included positive concordance (27.0%), negative concordance (5.36%) for BioFire PNplus Panel bacteria and viruses, and 16.73% for SOC specimens positive for non-BioFire PNplus Panel bacteria and viruses. 26.43% (651/2463) of specimens demonstrated partial concordance and 24.48% (603/2463) no concordance. Positive, partial, and negative concordances for BLS were 56.85%, 20.55%, and 22.59%, respectively, and 41.13%, 32.34%, and 26.35%, respectively, for SLS.
Table 3 Concordance of BioFire PNplus (PNplus) Panel and standard of care (SOC) results for all specimens, BAL-like specimens, and sputum-like specimens
Bacterial quantification by BioFire PNplus Panel and SOC
Semiquantitative results for BioFire PNplus Panel and SOC bacteria were compared for 1297 matched detections (Table 4). Mean differences between all three levels of SOC SRVs and BioFire PNplus Panel SRVs for all bacteria, BLS bacteria, and SLS bacteria were 1.06 (range 0.96–1.14), 1.34 (range 1.19 to 1.52), and 0.90 (range 0.71 to 1.14), respectively. For a subset of specimens (n = 903) with SOC quantitative culture results, mean difference between SOC SRV and BioFire PNplus Panel SRV for bacteria was 1.18. For specimens BioFire PNplus Panel positive and SOC negative, mean BioFire PNplus Panel SRVs for all bacteria, BLS bacteria, and SLS bacteria were 3.21, 3.10, and 3.27, respectively. Using this subset of BioFire PNplus Panel positive/SOC negative results, if a threshold for BLS reporting was set at BioFire PNplus Panel bin values of 104, 105, 106, or ≥ 107, then 482, 290, 158, and 77 BioFire PNplus Panel bacteria results, respectively, would be reported as positive and discordant with SOC. If a threshold for SLS reporting was set at BioFire PNplus Panel bin values of 104, 105, 106, or ≥ 107, then 834, 540, 336, and 177 bacteria results, respectively, would be reported as discordant with SOC. Therefore, increasing the BioFire PNplus Panel bin threshold for reporting bacteria as detected would result in increased concordance with SOC reported as culture negative. Establishment of reporting guidelines in consideration of both BioFire PNplus Panel bin values and the inherent log value differences between BioFire PNplus Panel results and SOC results improve overall concordance of bacteria reporting.
Table 4 Comparison of standard of care (SOC) bacteria standard reference values (SRV) and BioFire Pneumonia plus (PNplus) Panel bacteria standard reference values
SOC SRVs and BioFire PNplus Panel SRVs were equivalent for 25.37% of all bacteria, 19.38% of BLS bacteria, and 31.92% of SLS bacteria (Table 5). BioFire PNplus Panel SRVs were greater than SOC SVRs for 69.55% of all bacteria, 76.28% of BLS bacteria, and for 62.88% of SLS bacteria, with majority of BioFire PNplus Panel SRVs 1–2 logs greater than SOC SVRs. SOC SVRs were greater than BioFire PNplus Panel SRVs for 5.09% of all bacteria, 4.34% of BLS bacteria, and 5.83% of SLS bacteria, with majority demonstrating a one log difference.
Table 5 Distribution of standard of care (SOC) bacteria standardized reference values (SRV) and BioFire Pneumonia plus (PNplus) Panel bacteria standard reference values
Detection of MSSA and MRSA
A total of 531 specimens contained S. aureus, 97.93% (520/531) detected by BioFire PNplus Panel and 58.95% (313/531) detected by SOC (p ≤ 0.0001) with a concordance of 56.87% (Table 6). BioFire PNplus Panel did not detect 11 S. aureus (2.07%, all MSSA). A total of 24 specimens were reported to contain MSSA by SOC but were reported to contain MRSA by BioFire PNplus Panel and two specimens reported to contain MRSA by SOC were reported as MSSA by BioFire PNplus Panel. Mean SRVs for S. aureus detected by SOC, BioFire PNplus Panel, and detected only by BioFire PNplus Panel were 3.14, 4.18, and 2.92, respectively.
Table 6 Detection of methicillin sensitive Staphylococcus aureus (MSSA) and methicillin resistant S. aureus (MRSA) by BioFire Pneumonia plus (PNplus) Panel and standard of care (SOC)
Detection of gram-negative resistance markers
BioFire PNplus Panel detected in 1537 specimen bacteria (Acinetobacter baumannii-calcoaceticus complex, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus spp., P. aeruginosa, Serratia marcescens) for which ESBL and/or carbapenemase resistance genes would be reported. Of these, 185 (12.04%) had a total of 229 resistance genes (blaCTX-M [n = 133)], blaKPC [n = 67], blaIMP [n = 1], blaNDM [n = 2], blaVIM [n = 26]). Six blaOXA-48-like genes were detected in 1029 specimens (0.58%) positive by BioFire PNplus Panel for one or more of the following: E. cloacae complex, E. coli, K. aerogenes, K. oxytoca, K. pneumoniae group, Proteus spp., or S. marcescens. One resistance gene was detected in 76.76% (142/185) of specimens, two in 20.0% (37/185), and three in 3.24% (6/185). Due to large variations and inconsistencies in reporting of SOC phenotypic/genetic susceptibility data, no comparisons could be made.