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Table 4 Comparison of Analytic Approaches Using Data on Delirium and Interleukin-6 (IL-6)

From: Methodologic considerations in the design and analysis of nested case-control studies: association between cytokines and postoperative delirium

  Number of Subjects PREOP PACU POD2
(a) Matched Analysis of Delirium as the Outcome vs IL-6 as the Outcome
Matched Analysisa
 Delirium as the Outcome 78 (39:39)    
 Beta (SE)   0.00745 (0.0112) 0.00321 (0.00327) 0.0154 (0.0054)
P-value   0.508 0.326 0.005
 Odds Ratio (95% CI)   1.01 (0.99–1.03) 1.00 (0.99–1.01) 1.02 (1.01–1.03)
Matched Analysisb
 IL-6 as the Outcome 78 (39:39)    
 MPD   1.11 9.13 50.44
P-value   0.475 0.123 0.005
(b) Matched Analysis Using Observed IL-6 vs. Unmatched Analysis Using Simulated IL-6
Unmatched Analysis
 Simulated IL-6c 192 (49:143)    
 Beta (SE)   -0.0385 (0.0322) 0.00323 (0.002) 0.0176 (0.004)
P-value   0.231 0.105 0.0001
 Odds Ratio (95% CI)   0.96 (0.90–1.03) 1.00 (0.99–1.01) 1.02 (1.01–1.03)
Matched Analysis
 Observed IL-6d 78 (39:39)    
 Beta (SE)   0.00745 (0.0112) 0.00321 (0.00327) 0.0154 (0.0054)
P-value   0.508 0.326 0.005
 Odds Ratio (95% CI)   1.01 (0.99–1.03) 1.00 (0.99–1.01) 1.02 (1.01–1.03)
  1. aThe coefficients (Beta and SE), p-values, and odds ratios came from the conditional logistic regression where delirium case was the outcome, and IL-6 the independent variable
  2. bThe MPD (median paired differences) is the median of the paired differences (concentration level of IL-6 from the delirium case minus that of the control) within each time period. The p-values came from the nonparametric signed rank test
  3. PREOP preoperative, PACU post-anesthesia care unit, POD2 postoperative day 2, SE standard error, CI confidence interval
  4. cThe coefficients (Beta, SE), p-values, and odds ratios came from the unconditional multivariable logistic regression with delirium case as the outcome, and the six match factors as independent variables
  5. dThe coefficients (Beta, SE), p-values, and odds ratios came from the conditional logistic regression where delirium case is the dependent variable, and IL-6 the independent variable
  6. PREOP preoperative, PACU post-anesthesia care unit, POD2 postoperative day 2, SE standard error, CI confidence interval