. 2021 Jun 28;31(6):1833–1842. doi: 10.1111/ina.12899

TABLE 1.

Quantitative assessment method of nosocomial infection risk

Type	Intent	Method	Lower limit/ Sensitivity	Correlation	Sampling analysis time	Price
Direct measurement	Detecting viral RNA (ORF1ab, N and E) in the air or on the surface	Quantitative RT‐PCR	0.2 copies/μl (Sansure Biotech, Hunan, China) ³³	Strong: detect pathogens	1.0 ~ 2.0 h (h)	$3 for SARS‐CoV−2 test kit& $50 000 for real‐time PCR system
Direct measurement		ddPCR	0.109 copies/μl for ORF1ab, 0.42 copies/μl for N (Bio‐Rad) ³⁰	Strong: detect pathogens	1.5 ~ 4.0 h	$ 200 000 (Bio‐Rad QX200)
Surrogate	Monitoring microorganisms in the environment	Cell culture and colony counting	‐	Weak: little correlation between culturable/ active microbes and pathogens	>24.0 h	$50
	Monitoring microorganisms in the environment	ATP fluorescence detection	1 × 10⁻¹⁶ mol/ATP (Hygiena EnSURE ATP Test Luminometer)		1 s	$5,000 (Hygiena EnSURE ATP Test Luminometer)
	Monitoring CO₂ concentration	Infrared CO₂ sensors	±50 ppm (iBEEM)	Moderate: characterize exhaled breath	5 min	$400 (iBEEM)

Abbreviations: ATP, adenosine triphosphate; CO₂, carbon dioxide; ddPCR, droplet digital PCR; E, the envelope protein; N, the Nucleocapsid protein gene; ORF1ab, open reading frame 1ab; RNA, ribonucleic acid; RT‐PCR, reverse transcription‐polymerase chain reaction.