Table 3.

Mean times required to obtain first positive molecular result compared to mean times required to obtain Gram stain result or final identification from corresponding physician-ordered blood culture

Bacterial grouping	Result (mean h ± SD) for:				P by t test
	PCR/pyrosequencing		Physician-ordered blood culture
	First positive time pointd (n = 89)	TATb for MDxc IDd (n = 89)	TAT for Gram staine (n = 76)	TAT for phenotypic culture ID (n = 92)
Staphylococcus spp.	5.9 ± 2.8	11.9 ± 2.8	31.8 ± 12.9	81.6 ± 24.0	<0.001
Streptococcus spp.	5.0 ± 0.2	11.0 ± 0.2	26.3 ± 16.6	79.2 ± 24.0	<0.001
Enteric GNRsa	7.1 ± 5.7	13.1 ± 5.7	20.3 ± 7.5	81.6 ± 24.0	<0.001
All bacteria	5.8 ± 2.9	11.8 ± 2.9	27.9 ± 13.6	81.6 ± 24.0	<0.001

^aGNRs, Gram-negative rods.

^bTAT, turnaround time.

^cMDx, molecular.

^dFor the purposes of these calculations, 3 outliers were excluded from this analysis, including 1 each of a Staphylococcus sp., a Streptococcus sp., and an enteric GNR species, which were detected and accurately identified by PCR/pyrosequencing only from the final 5-day-time-point aliquot.

^eElectronic medical records from 11 of the physician-ordered, culture-confirmed positive blood culture bottles lacked documentation for the specific time that the Gram stain result was called to the unit and were therefore excluded from this analysis. For the purposes of these calculations, 5 outliers were excluded from this analysis, including 3 Staphylococcus isolates, with Gram stain times of 61.2, 123.3, and 121.9 h, and 2 Streptococcus isolates, with Gram stain times of 76.2 and 66.6 h. Removal of these 5 outliers was considered acceptable because the adjusted mean times to Gram stain were not appreciably different from the calculated medians.