Table S1. Definitions of organ dysfunction according to the Sepsis-2 criteria
Organ system Organ dysfunction criteria Central nervous
system
Agitated
Confused
Drowsy
Unconscious Cardiovascular
system
Systolic blood pressure <90 mmHg
Decrease in systolic blood pressure >40 mmHg
Mean arterial pressure <70 mmHg
Need for vasopressors due to circulatory failure Respiratory
dysfunction
SaO2 <90%
Need for mechanical ventilation
PaO2/FiO2 <300 (calculated for non-COPD patients with SaO2 90- 94% and use of oxygen)
PaO2/FiO2 <250 (calculated for patients with COPD with SaO2 87- 95% and use of oxygen)
Renal dysfunction Creatinine >177
mol/L (in the absence of prior renal dysfunction) Increase of creatinine >44
mol/L Urinary output <0.5ml/kg/hour for 2 hours Hematological
dysfunction
Platelets <100 × 109/L
INR>1.5 (in the absence of anticoagulants) Hepatic Bilirubin >70 μmol/L
The estimation of FiO2 was done according to supplement table 2 (table S3) The Severinghausen equation was used to calculate the PaO2 (25).
Table S2. Calculation of SOFA-scores
SOFA score
Organ system 1 2 3 4
Respiration SaO2 % without O2
PaO2/FiO2 mmHg
<96
<400
<92
<300
with mechanical ventilation
<200 <100 Coagulation Platelets x109/L <150 <100 <50 <20
Liver Bilirubin μmol/L >19 >32 >101 >204
Cardiovascular MAP <70 <70 &
vasopressor
n/a n/a
Renal Creatinine μmol/L >110 >170 >299 >440
Central Nervous
Altered Mental status
n/a n/a n/a
1 SOFA score for coagulopathy, respiratory, renal, or liver dysfunction could only be obtained if the patient was not suffering from a malignancy, respiratory, renal or liver disease, respectively.
If the patient was treated with oxygen, the Severinghausen formula was used to estimate PaO2/FiO2
Table S3. Table for estimating FiO2 dependent on administered O2 flow.
O2 flow (l/min) Estimated FiO2 (%)
0 21
1 22
2 24
3 26
4 28
5 35
6 37
7 40
8 52
9 56
Table S4. Characteristics of the study population group by site.
N Lund 1 N = 65
Bern N = 95
Vancouver N = 70
Helsingborg N = 95
Lund 2 N = 199
Combined N = 524
p-value
Likelihood of infection 524 <0.0001
Infection 11% (7) 23% (22) 14% (10) 29% (28) 15% (29( 18% (96)
Probable infection 9% (6) 11% (10) 21% (15) 22% (21) 16% (32) 16% (84)
Virus 22% (14) 7% (7) 3% (2) 0% (0) 8% (16) 7% (39)
Probably NOT infection 17% (11) 8% (8) 16% (11) 13% (12) 14% (27) 13% (69)
No infection 42% (27) 51% (48) 46% (32) 36% (34) 48% (95) 45% (236)
Age 524 75.0 (58.2–83.5) 68.0 (54.5–76.0) 54.7 (43.4–
71.0)
77.3 (65.6–85.1) 74.5 (64.6–83.5) 72.2 (58.0–82.0) <0.00001
Females 524 54% (35) 45% (43) 50% (35) 48% (46) 49% (97) 49% (256) 0.88
Medications
Warfarin 520 17% (11) 17% (16) 6% (4) 18% (17) 25% (50) 19% (98) 0.006
Steroids before admission 520 9% (6) 18% (17) 13% (9) 5% (5) 10% (19) 11% (56) 0.07
Heparin/LMWH before admission
519 2% (1) 6% (6) 1% (1) 1% (1) 4% (7) 3% (16) 0.28
Immunosuppression before admission
520 3% (2) 0% (0) 6% (4) 1% (1) 3% (6) 2% (13) 0.13
Comorbidities
Diabetes 524 20% (13) 29% (28) 14% (10) 15% (14) 19% (38) 20% (103) 0.09
Cardiovascular 524 51% (33) 60% (57) 36% (25) 38% (36) 49% (98) 48% (249) 0.008
Renal 524 14% (9) 37% (35) 16% (11) 5% (5) 10% (19) 15% (79) <0.00001
Respiratory 524 26% (17) 17% (16) 9% (11) 21% (20) 32% (63) 26% (137) 0.053
COPD 524 11% (7) 1% (1) 13% (9) 13% (12) 19% (38) 13% (67) 0.00008
Liver 524 0% (0) 9% (9) 9% (6) 0% (0) 2% (4) 5% (24) <0.00001
Malignancy 524 14% (9) 15% (14) 6% (4) 17% (16) 9% (18) 12% (63) 0.24
Immunodeficiency 524 2% (1) 0% (0) 30% (21) 1% (1) 2% (3) 2% (9) 0.09
No comorbidities 524 28% (18) 23% (22) 13% (9) 32% (30) 28% (56) 28% (147) 0.76
Outcome
ICU-admittance within 72 hours
524 3% (2) 35% (33) 9% (6) 4% (4) 5% (9) 10% (54) <0.00001
Mortality within 72 hours 524 5% (3) 7% (7) 0% (0) 4% (4) 5% (9) 4% (23) 0.20
Positive blood culture 524 0% (0) 15% (14) 7% (5) 14% (13) 5% (10) 8% (42) 0.0005
SOFA score at inclusion 524 1 (0–2) 2 (1–3) 1 (0–2.75) 2 (1–3) 1 (0–2) 1 (0–3) 0.001
Number of dysfunctional organs
524 <0.00001
0 48% (31) 14% (13) 29% (20) 25% (24) 45% (89) 34% (177)
1 35% (23) 27% (26) 34% (24) 31% (29) 25% (49) 29% (151)
2 6% (4) 27% (26) 16% (11) 28% (27) 17% (33) 19% (101)
3 3% (2) 11% (10) 11% (8) 7% (7) 8% (15) 8% (42)
4 3% (2) 9% (9) 4% (3) 2% (2) 2% (3) 4% (19)
5 0% (0) 3% (3) 1% (1) 1% (1) 0% (0) 1% (5)
6 0% (0) 1% (1) 4% (3) 0% (0) 0% (0) 1% (4)
7 5% (3) 7% (7) 0% (0) 5% (5) 5% (10) 5% (25)
Diagnoses 524
Infections
Central nervous 0% (0) 0% (0) 0% (0) 1% (1) 0% (0) 0% (1)
COPD exacerbation 2% (1)0% (0) 0% (0) 6% (4) 1% (1) 4% (7) 2% (13)
Endocarditis 3% (2) 3% (3) 1% (1) 0% (0) 0% (0) 1% (4)
Gastrointestinal 2% (1) 1% (1) 3% (2) 3% (3) 4% (8) 3% (16)
Genitourinary 14% (9) 11% (10) 1% (1) 17% (16) 4% (8) 7% (36)
Influenza 3% (2) 3% (3) 0% (0) 0% (0) 3% (6) 3% (18)
Other infection 0% (0) 0% (0) 4% (3) 2% (2) 2% (4) 2% (11)
Respiratory 2% (1) 11% (10) 16% (11) 23% (22) 16% (32) 16% (83)
Skin/soft tissue 5% (3) 3% (3) 3% (2) 2% (2) 2% (3) 2% (11)
Unspecified sepsis 2% (1) 5% (5) 3% (2) 2% (2) 2% (4) 16% (83)
Viral 5% (3) 4% (4) 1% (1) 0% (0) 3% (5) 2% (10)
Non-infectious causes
Acute myocardial infarction 0% (0) 2% (2) 0% (0) 1% (1) 0% (0) 1% (3)
Cerebrovascular 0% (0) 12% (11) 0% (0) 2% (2) 2% (4) 3% (17)
CNS 2% (1) 0% (0) 1% (1) 0% (0) 1% (2) 1% (4)
Diabetes 0% (0) 1% (1) 0% (0) 2% (2) 1% (2) 1% (5)
Gastro 2% (1) 6% (6) 16% (11) 2% (2) 5% (10) 6% (30)
Head trauma 0% (0) 3% (3) 0% (0) 2% (2) 0% (0) 1% (5)
Heart rhythm 12% (8) 8% (8) 3% (2) 6% (6) 11% (22) 9% (46)
Intoxication 0% (0) 2% (2) 3% (2) 4% (4) 2% (3) 2% (11)
Kidney 3% (2) 0% (0) 3% (2) 0% (0) 2% (3) 1% (7)
Liver 0% (0) 1% (1) 0% (0) 0% (0) 0% (0) 0% (1)
Lung 6% (4) 4% (4) 7% (5) 6% (6) 10% (20) 7% (39)
Lung embolic 6% (4) 2% (2) 0% (0) 2% (2) 1% (2) 2% (10)
Orthopedic 2% (1) 5% (5) 4% (3) 2% (2) 2% (3) 3% (14)
Other 15% (10) 2% (2) 17% (12) 5% (5) 18% (36) 12% (65)
Seizures 6% (4) 2% (2) 1% (1) 7% (7) 1% (1) 2% (13)
Unspecified heart 2% (1) 7% (7) 4% (3) 0% (0) 6% (11) 6% (29)
Vascular 3% (2) 0% (0) 9% (6) 4% (4) 2% (3) 1% (69)
Continuous variables are displayed with median and inter-quartile range. Categorical variables are displayed with proportions and numbers within brackets.
Non-categorical variables (Age, SOFA, Number of OD) are tested with Kruskal-Wallis tests and categorical variables with Pearson's chi-squared test or Fisher’s exact test, as appropriate.
Table S5. Discriminatory Values of Biomarkers for infection-induced organ dysfunction among all patients (n=524)
The whole cohort (group I-V, n=524) was included in this analysis, thus including probable cases which potentially could be misclassified. In this analysis patients with probable infection were regarded as infected whereas patients with viral disease or probable not infectious causes were regarded as not infected. AUC, Sensitivity, specificity, positive and negative likelihood ratio, positive predictive value and negative predictive value was calculated. The cut-off value from the analysis in table 2 was used. The prevalence of infection-induced organ dysfunction was 26%
n AUC Cut-off Sens Spec LR+ LR- PPV NPV
HBP 524 0.73 (0.68-0.78) 13.7 0.55 (0.46-0.64) 0.80 (0.76-0.84) 2.76 (2.15-3.55) 0.56 (0.46-0.68) 0.49 (0.41-0.57) 0.84 (0.80-0.87) HBP 524 0.73 (0.68-0.78) 15 0.52 (0.43-0.61) 0.83 (0.78-0.86) 3.0 (2.29-3.92) 0.58 (0.48-0.69) 0.51 (0.42-0.59) 0.83 (0.79-0.87) HBP 524 0.73 (0.68-0.78) 30 0.28 (0.20-0.36) 0.95 (0.93-0.97) 5.98 (3.53-10.14) 0.76 (0.68-0.84) 0.67 (0.53-0.79) 0.79 (0.75-0.83) PCT 518 0.69 (0.64-0.74) 0.5 0.49 (0.40-0.58) 0.78 (0.73-0.82) 2.21 (1.71-2.86) 0.66 (0.66 -0.78) 0.43 (0.35-0.52) 0.82 (0.77-0.85) PCT 518 0.69 (0.64-0.74) 2 0.29 (0.21-0.37) 0.93 (0.90-0.95) 3.93 (2.51-6.14) 0.77 (0.69-0.86) 0.58 (0.45-0.70) 0.79 (0.75-0.83) WBC 524 0.65 (0.59-0.70) 10.8 0.60 (0.52-0.69) 0.63 (0.58-0.68) 1.65 (1.36-1.99) 0.62 (0.50-0.78) 0.36 (0.30-0.43) 0.82 (0.78-0.86) CRP 472 0.82 (0.78-0.86) 20.1 0.90 (0.83-0.94) 0.60 (0.55-0.66) 2.26 (1.96-2.61) 0.17 (0.10-0.29) 0.45 (0.39-0.52) 0.94 (0.90-0.97) Lactate 346 0.51 (0.44-0.58) 2.0 0.49 (0.38-0.59) 0.56 (0.50-0.63) 1.12 (0.87-1.44) 0.91 (0.72-1.14) 0.29 (0.22-0.37) 0.75 (0.68-0.81)
Table S6. Sensitivity analysis of the AUC for HBP in detecting infection-induced organ dysfunction.
Cohort Number of patients AUC (95% C.I)
Confidently adjudicated cases, group I and IV (table 2)
332 0.82 (0.76-0.87)
Confidently adjudicated cases including patients with hemolytic samples
426 0.79 (0.74-0.84)
All cases, group I-V (table S5) 524 0.73 (0.68-0.78)
All cases including patients with hemolytic samples
670 0.72 (0.67-0.76)
Lund 1 (confidently adjudicated cases) 34 0.88 (0.73-1)
Bern (confidently adjudicated cases) 70 0.78 (0.65-0.91)
Vancouver (confidently adjudicated cases) 42 0.85 (0.71-0.99)
Helsingborg (confidently adjudicated cases) 62 0.85 (0.75-0.96)
Lund 2 (confidently adjudicated cases) 124 0.80 (0.69-0.90)
Table S7. Discriminatory Values of Biomarkers for critical infection among all patients (n=524)
All patients (group I-V, n=524) were included in this analysis, thus including probable cases which potentially could be misclassified. In this analysis patients with probable infection were regarded as infected whereas patients with viral disease or probable not infectious causes were regarded as not infected. AUC, sensitivity, specificity, positive and negative likelihood ratio, positive predictive value and negative predictive value was calculated. The cut-off value from the analysis in table 3 was used. The prevalence of critical infection was 4%.
n AUC Cut-off Sensitivity (95% C.I)
Specificity (95% C.I)
LR+
(95% C.I)
LR- (95% C.I)
PPV (95% C.I)
NPV (95% C.I) HBP 524 0.87 (0.79-0.95) 15 0.83 (0.61, 0.95) 0.76 (0.72, 0.80) 3.48 (2.72, 4.44) 0.23 (0.09, 0.56) 0.14 (0.08, 0.21) 0.99 (0.97, 1.00) HBP 524 0.87 (0.79-0.95) 22.85 0.78 (0.56, 0.93) 0.86 (0.83, 0.89) 5.77 (4.24, 7.85) 0.25 (0.12, 0.55) 0.21 (0.13, 0.31) 0.99 (0.97, 1.00) HBP 524 0.87 (0.79-0.95) 30 0.65 (0.43, 0.84) 0.92 (0.89, 0.94) 8.17 (5.36, 12.45) 0.38 (0.22, 0.66) 0.27 (0.16, 0.41) 0.98 (0.97, 0.99) PCT 518 0.76 (0.65-0.87) 0.5 0.74 (0.52, 0.90) 0.73 (0.69, 0.77) 2.75 (2.07, 3.65) 0.36 (0.18, 0.71) 0.11 (0.07, 0.18) 0.98 (0.96, 0.99) PCT 518 0.76 (0.65-0.87) 2 0.43 (0.23, 0.66) 0.89 (0.86, 0.91) 3.84 (2.27, 6.51) 0.64 (0.44, 0.91) 0.15 (0.08, 0.26) 0.97 (0.95, 0.98) WBC 524 0.66 (0.52-0.79) 17.55 0.39 (0.20, 0.61) 0.91 (0.88, 0.93) 4.17 (2.34, 7.43) 0.67 (0.48, 0.93) 0.16 (0.08, 0.28) 0.97 (0.95, 0.98) CRP 472 0.81 (0.72-0.91) 120 0.65 (0.43, 0.84) 0.85 (0.82, 0.88) 4.44 (3.06, 6.44) 0.41 (0.23, 0.71) 0.19 (0.11, 0.29) 0.98 (0.96, 0.99) Lactate 346 0.69 (0.57-0.82) 2.65 0.59 (0.33-0.82) 0.79 (0.70-0.80) 2.36 (1.52-3.66) 0.55 (0.31-0.97) 0.11 (0.05-0.19) 0.97 (0.94-0.99)
Table S8. Sensitivity analysis of the AUC for HBP in detecting critical infection.
Cohort Number of patients AUC (95% C.I)
Confidently adjudicated cases, group I and IV (table 3)
332 0.88 (0.77-0.99)
Confidently adjudicated cases including patients with hemolytic samples
426 0.87 (0.77-0.96)
All cases, group I-V (table S7) 524 0.87 (0.79-0.95)
All cases including patients with hemolytic samples
670 0.85 (0.77-0.92)
Lund 1 (confidently adjudicated cases) 34 –– (no patients with critical infection)
Bern (confidently adjudicated cases) 70 0.81 (0.58-1)
Vancouver (confidently adjudicated cases) 42 1
Helsingborg (confidently adjudicated cases) 62 0.88 (0.73-1)
Lund 2 (confidently adjudicated cases) 124 0.96 (0.90-1)
Table S9. Characteristics of patients with HBP>30 ng/mL but no critical infection
Patients confidently adjudicated to have presented with infection or non-infectious cause of illness but no critical infection (n=320).
Differences between patients with HBP above or below 30ng/mL were assessed for infected and non-infected patients separately using Fisher’s exact test. Admittance to ICU and mortality was not assessed for infected patients since these are part of the definition of critical infection.
No critical infection HBP>30
n=26
No critical infection HBP<30
n=294
p-value
Infection 18 (69.3%) 66 (22.4%) <0.00001
Infection n=18
No infection n=8
Infection n=66
No infection n=228
Infection No infection
Positive blood culture 11 (61%) - 24 (36%) - 0.10 -
Sex (female) 7 (39%) 1 (13%) 33 (50%) 116 (51%) 0.44 0.07
Outcome
Organ dysfunction 15 (83%) 7 (88%) 49 (74%) 142 (62%) 0.54 0.26
Critical care -* 3 (38%) -* 22 (10%) -* 0.04
Mortality (3 days) -* 3 (38%) -* 9 (4%) -* 0.005
Comorbidities
Diabetes 2 (11%) 1 (13%) 14 (21%) 39 (17%) 0.50 1
Cardiovascular 8 (44%) 4 (50%) 34 (52%) 108 (47%) 0.79 1
Renal disease 8 (44%) 2 (25%) 12 (18%) 27 (12%) 0.03 0.26
Respiratory disease 5 (28%) 2 (25%) 17 (26%) 46 (20%) 1 0.67
Liver disease 2 (11%) 0 (0%) 6 (9%) 8 (4%) 0.68 1
Malignancy 4 (22%) 0 (0%) 8 (12%) 27 (12%) 0.28 0.60
Immunodeficiency 0 (0%) 0 (0%) 2 (3%) 3 (1%) 1 1
Diagnosis
Infection diagnosis
Respiratory infection 5 (28%) - 38 (58%) - 0.03 -
Genitourinary infection 7 (39%) - 15 (23%) - 0.23 -
Unspecified sepsis 3 (17%) - 3 (5%) - 0.11 -
Skin/soft tissue 1 (6%) - 4 (6%) - 1 -
Endocarditis 0 (0%) - 3 (5%) - 1 -
Other infection 2 (12%) - 3 (5%) - 0.29 - Non-infection diagnosis
Heart rhythm - 0 (0%) - 46 (20%) - 0.36
Gastrointestinal - 0 (0%) - 24 (11%) - 1
Other heart diagnosis - 2 (25%) - 19 (8%) - 0.15
Cerebrovascular - 1 (12%) - 14 (6%) - 0.41
Acute myocardial infarction
- 1 (12%) - 2 (1%) - 0.10
Liver - 1 (12%) - 0 (0%) - 0.03
Lung - 1 (12%) - 12 (5%) - 0.37
Orthopedic - 1 (12%) - 12 (5%) - 0.37
Vascular - 1 (12%) - 5 (2%) - 0.19
Other - 0 (0%) - 94 (41%) 0.02