Definitions
Community-acquired pneumonia (CAP) was defined as an acute pulmonary infection
with an onset before or within 48 hrs from hospital admission and acquired outside a healthcare
setting (7, 8).
Hospital-acquired pneumonia (HAP) was defined as a pulmonary infection in
nonmechanically ventilated patients that was not incubating at the time of admission and
occurred ≥48 hrs after admission (1).
Ventilator-associated pneumonia (VAP) was defined as a pulmonary infection arising in
≥48 hrs after endotracheal intubation with no evidence of pneumonia at the time of intubation or
the diagnosis of a new pulmonary infection if the initial admission to ICU was for pneumonia
(1).
Very early onset VAP (VE-VAP) was defined as pulmonary infection arising within 48 hrs
of intubation that was not incubating at the time of intubation (16).
Early-onset VAP was defined as VAP with onset >48 hrs but <5 days after intubation (1).
Late-onset VAP was defined as VAP with onset _5 days after intubation (6).
Severity of Infection
Severity of sepsis was defined as sepsis, severe sepsis, or septic shock following the
American College of Chest Physicians/Society of Critical Care Medicine 1992 conference. To
qualify for severe sepsis, new or worsening organ dysfunction other than the lung must be
present and related to the episode of pneumonia (14).
Definite etiology was defined as a microorganism isolated in a patient with suspicion of
pneumonia from blood or respiratory sample and judged as definite by the attending physician.
Cultures with normal flora, Staphylococcus epidermidis or coagulase-negative staphylococci,
and Candida species were considered to be nonpathogenic; these cultures and those thatshowed
no growth were classified as negative cultures for purposes of analysis.
Organ dysfunction was defined according to Sepsis-related Organ Failure Assessment
definitions (15).
Contribu tion of pneumonia to death was defined according to the attending physician,
who determined whether pneumonia was: 1) directly related to death; 2) a contributing factor for
death; or 3) unrelated to the fatal outcome.
Comorbidities
Nonmetastatic cancer could include regional lymph nodes.
Chronic renal failure was defined as chronic renal supportive therapy (i.e., chronic
hemodialysis, hemofiltration, or peritoneal dialysis) for irreversible renal disease or history of
chronic renal insufficiency associated with clinical adverse effects (usually creatinine >300
μmol/L).
COPD was defined as chronic obstructive pulmonary disease, chronic bronchitis, or
emphysema requiring prescribed treatment.
Chronic respiratory failure was defined as permanent shortness of breath on light
activity, attributable to pulmonary (chronic restrictive or obstructive) disease. The subject is
unable to work, climb stairs, or perform household duties. There is documented chronic
hypoxemia, hypercarbia, secondary polycythemia, severe pulmonary hypertension (mean
pulmonary artery pressure >40 mm Hg), or requirement for chronic respiratory support (e.g.,
home oxygen therapy).
Chronic heart failure was defined as fatigue, dyspnea, or angina either at rest or with a
minimum level of activity. The subject cannot stand alone, walk slowly, or dress without
symptoms (i.e., New York Heart Association class IV).
Cirrhosis was diagnosed either by biopsy taken before or during ICU admission or by
clinical features such as portal hypertension, presence of esophageal/gastric varices
(demonstrated by surgery, imaging, or endoscopy), or the demonstration of retrograde splenicvenous flow by ultrasound, or history of variceal bleeding, or episodes of acute hepatic
failure/encephalopathy/coma.
Alcoholism was defined as alcohol intake that exceeds the social drinking custom (usually
regular intake of >80 g of alcohol per day for at lest 6 months before ICU admission) and that
was responsible for clinical adverse effects such as logorrhea, encephalopathy, neurologic
disorder, nutritional disorder, and cirrhosis.
Homelessness was defined as no fixed address for 6 months before ICU admission.
Drug abuse was defined as drug addiction with intravenous drugs (opioids and
derivatives) for ≥6 months before ICU admission.
Diabetes mellitus was defined as diabetes that required daily insulin therapy.
Solid organ transplant was defined as liver, heart, lung, or kidney transplant still
requiring immunosuppression. Immunosuppression can be associated with the following:
1. Known daily corticosteroid therapy with a total daily dose ≥1 mg/kg or >40 mg/day of oral
prednisolone for ≥7 consecutive days within 1 month before study entry.
2. Clinically suspected or known AIDS as defined by the U.S. Centers for Disease Control and
Prevention.
3. Granulocyte count <1  109/L attributable to a cause other than severe sepsis (e.g., metastatic
or hematologic malignancies or chemotherapy).
4. Immunosuppressant therapy (e.g., attributable to an organ or bone marrow transplant).
McCabe’s Classification of Chronic Disease (12)
Each of the preceding comorbidities, if present, should be coded according to this classification:
1. Nonfatal underlying disease or no underlying disease (all patients other than the ones
categorized subsequently).
2. Ultimately fatal (<5 yrs) underlying disease: examples include bone marrow aplasia, chronic
leukemia; myeloproliferative syndrome; myeloma; malignant lymphoma less than stage IV;
transplantation of heart, lung, bone marrow, pancreas, or liver; cancer without metastasis; portal
hypertension; cardiac insufficiency (New York Heart Association III); chronic respiratory
insufficiency with oxygen therapy; chronic hemodialysis; and AIDS classification IV, A, B, or E.
3. Rapidly fatal (_1 yr) underlying disease: examples include acute leukemia, primitive or blastic
transformation
of chronic myeloid leukemia, malignant lymphoma or Hodgkin’s disease stage IV, metastatic
cancer, hepatic failure with encephalopathy, ischemic or nonobstructive cardiac failure New
York Heart Association IV, rapidly progressive respiratory failure, AIDS classification IV, C, or
D, and HIV encephalopathy.