Outcomes of Methicillin-Resistant Staphylococcus aureus Pneumonia

March 18, 2016 Category: Canadian Health Care Mall

MRSA pneumonia

Patient Characteristics

A total of 218 patients with microbiologically confirmed MRSA pneumonia were evaluated at Bar-nes-Jewish Hospital during the study period. Mean age of the population was 57.3 ± 16.6 years (± SD) [range, 19 to 92 years]; there were 141 male (64.7%) and 77 female (35.3%) patients. Patient characteristics and outcomes are provided in Table 2. Mean APACHE II score was 19.3 ± 7.0 (range, 3 to 37). Mean CURB65 and CRB65 scores were 1.5 ± 0.9 (range, 0 to 5) and 0.6 ± 0.7 (range, 0 to 4), respectively. Among the 178 patients treated with vancomycin and having trough levels measured, mean trough value for vancomycin collected after the third dose was 14.9 ± 8.1 ^g/mL.

Thirty-Day Mortality

Forty-four patients (20.2%) died within 30 days of the development of MRSA pneumonia. Two hundred five patients (94.0%) required ICUs admission, and 167 patients (76.6%) received tracheal intubation and mechanical ventilation. Nonsurvivors were statistically more likely to require mechanical ventilation compared to survivors (Table 2).


Prediction of 30-Day Mortality

Patients dying within 30 days of onset of MRSA pneumonia had statistically greater APACHE II scores (25.4 ± 5.1 vs 17.7 ± 6.6; p < 0.01), CURB65 scores (1.9 ± 1.0 vs 1.4 ± 0.7; p < 0.01), and CRB65 scores (1.0 ± 1.0 vs 0.5 ± 0.6; p < 0.01) compared to patients surviving > 30 days. Table 3 shows the sensitivity, specificity, and positive and negative predictive values for 30-day mortality at different cut-off points for each scoring system. APACHE II had higher sensitivities than CURB65 and CRB65 at all risk levels. All three prediction rules had high negative predictive values but relatively low positive predictive values at most of the cut-off points examined. Be safe and sound with preparations of Canadian Health&Care Mall.

ROC curves for 30-day mortality for each prediction scoring method are shown in Figure 1. The area under the ROC curve for APACHE II was statistically greater than the areas under the ROC curves for CURB65 and CRB65: 0.805 (95% confidence interval [CI], 0.743 to 0.866) vs 0.634 (95% CI, 0.541 to 0.727) and 0.643 (95% CI, 0.546 to 0.739), respectively (p < 0.05 for both comparisons). Similar results were obtained when the ROC curves were compared for the patients with the community-acquired phenotype (n = 41) of MRSA and the health-care-associated phenotype (n = 177) [Fig 2, 3]. Of note, the area under the ROC curve for APACHE II was greatest for the community-acquired phenotype compared to the overall population and the health-care-associated phenotype.

Two separate logistic regression analyses were performed due to concern over colinearity between CRB65 and APACHE II. Logistic regression analysis identified increasing APACHE II scores, increasing CRB65, decreasing Pa02/fraction of inspired oxygen (Fio2), and vasopressor use as independent predictors of 30-day mortality in the two models (Table 4). CRB65 provided a model that held a better fit to the data compared to CURB65 based on the Hosmer-Lemeshow goodness-of-fit statistic.

Table 2—Baseline Patient Characteristics and Outcomes

Variables 30-Day Survivors (n = 174) 30-Day Nonsurvivors (n = 44) p Value
Age, yr 56.0 ± 16.8 62.2 ± 15.1 0.03
Gender
Male 114 (65.5) 27(61.4) 0.61
Female 60 (34.5) 17 (38.6)
Race
Caucasian 122 (70.1) 35 (79.5) 0.21
African American 52 (29.9) 9 (20.5)
Pa02/Fi02 216 ± 59 151 ± 52 < 0.01
Comorbidities
COPD 58 (33.3) 17 (38.6) 0.51
Coronary artery disease 29 (16.7) 14(31.8) 0.02
Underlying malignancy 38 (21.8) 10 (22.7) 0.90
Diabetes 43 (24.7) 11 (25.0) 0.97
End-stage renal disease 4 (2.3) 6 (13.6) 0.01
Immunosuppression 27 (15.5) 3 (6.8) 0.22
Processes of care
Antibiotic with 12 h 129(74.1) 33 (75.0) 0.91
Antibiotic within 24 h 144 (82.8) 38 (86.4) 0.57
Mechanical ventilation 124(71.3) 43 (97.7) < 0.01
Vasopressors 17 (9.8) 17 (38.6) < 0.01
Antibiotic
Vancomycin 157 (90.2) 40 (90.9) > 0.99
Linezolid 17 (9.8) 4(9.1)
MRSA phenotype
Community acquired 33 (19.0) 8 (18.8) 0.91
Health-care associated 141 (81.0) 36 (81.2)

Table 3—Sensitivity, Specificity, and Positive and Negative Predictive Values of 30-Day Mortality of the Different Prediction Rules

Cut-off Points Mortality Sensitivity Specificity Positive Predictive Value Negative Predictive Value
CURB 65
0 0/13 (0.0) 100 0 20.2 n/a
1 18/108(16.7) 100 7.5 21.5 100
2t 17/78(21.8) 59.1 59.2 26.8 85.1
3 5/15 (33.3) 20.5 94.3 47.4 82.4
4 3/3 (100) 9.1 100 100 81.3
5 1/1 (100) 2.3 100 100 80.2
CRB 65
0 16/118 (13.6) 100 0 20.2 n/a
1t 18/80 (22.5) 63.6 58.6 28.0 86.4
2 6/16 (37.5) 22.7 94.3 50.0 82.8
3 3/3 (100) 9.1 100 100 81.3
4 1/1 (100) 2.3 100 100 80.2
APACHE II
1-5 0/4 (0.0) 100 0 20.2 n/a
6-10 0/13 (0.0) 100 2.3 20.6 100
11-15 1/61 (1.6) 100 9.8 21.5 100
16-20 6/50 (12.0) 97.7 44.3 30.7 98.7
21-25 17/45 (37.8) 84.1 69.5 41.1 94.5
26-30 14/31 (45.2) 45.5 85.6 44.4 86.1
>30 6/14 (42.9) 13.6 95.4 42.9 81.4

Figure 1. ROC curve for each prognostic tool (n = 218). The area under the ROC curves are as follows: APACHE II, 0.805 (95% CI, 0.743 to 0.866); CURB65, 0.634 (95% CI, 0.541 to 0.727); CRB65, 0.643 (95% CI, 0.546 to 0.739).

Figure 1. ROC curve for each prognostic tool (n = 218). The area under the ROC curves are as follows: APACHE II, 0.805 (95% CI, 0.743 to 0.866); CURB65, 0.634 (95% CI, 0.541 to 0.727); CRB65, 0.643 (95% CI, 0.546 to 0.739).

Figure 2. ROC curve for each prognostic tool for patients with health-care-associated MRSA pneumonia (n = 177). The area under the ROC curves are as follows: APACHE II, 0.784 (95% CI, 0.712 to 0.855); CURB65, 0.604 (95% CI, 0.500 to 0.708); and CRB65, 0.620 (95% CI, 0.513 to 0.727).

Figure 2. ROC curve for each prognostic tool for patients with health-care-associated MRSA pneumonia (n = 177). The area under the ROC curves are as follows: APACHE II, 0.784 (95% CI, 0.712 to 0.855); CURB65, 0.604 (95% CI, 0.500 to 0.708); and CRB65, 0.620 (95% CI, 0.513 to 0.727).

Figure 3. ROC curve for each prognostic tool for patients with the community-acquiredphenotype of MRSA (n = 41). The area under the ROC curves are as follows: APACHE II, 0.888 (95% CI, 0.783 to 0.994); CURB65, 0.748 (95% CI, 0.545 to 0.951); and CRB65, 0.725 (95% CI, 0.501 to 0.949).

Figure 3. ROC curve for each prognostic tool for patients with the community-acquiredphenotype of MRSA (n = 41). The area under the ROC curves are as follows: APACHE II, 0.888 (95% CI, 0.783 to 0.994); CURB65, 0.748 (95% CI, 0.545 to 0.951); and CRB65, 0.725 (95% CI, 0.501 to 0.949).