Table 4.

Challenges for high-quality studies in the infectious diseases field, in ICU patients and in HAP/VAP

Infectious diseases	Low number of patients
	Different clinical presentation of pathologies
	Different diagnostic algorithms
Intensive care unit (ICU)	Low number of patients
	Critically ill patients, severe patients
	Case mix
	Altered pharmacokinetics in critically ill patients
	Altered consciousness of patients
	Difficult to generalize findings from studies with different populations
HAP/VAP	No definite diagnostic algorithm
	Different microbiology in etiology (national, hospital, ward, and ICU scale)
	Different antibiotic susceptibility patterns (national, hospital, ward, and ICU scale)
	Difficult to generalize findings from studies with different populations