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Table 6 Predictors of hospital length of stay during diagnosis and treatment of active TB, stratified by timing of hospitalization, Montreal, January 1996 -- May 2007

From: Predictors of hospitalization of tuberculosis patients in Montreal, Canada: a retrospective cohort study

  Initial hospitalizations
(n = 1006)
Hospitalizations during treatment (n = 206)
Characteristics Crude HR
(95% CI)
Adjusted HRa,b
(95% CI)
Crude HR
(95% CI)
Adjusted HRa
(95% CI)
Sex
 Male 1.01 (0.89–1.14) - 1.29 (0.78–2.11) -
 Female 1.00   1.00  
Age in yearsc     0.99 (0.98–1.00)
 log(LOS) ≤ 2.5 1.02 (1.02–1.03) 1.02 (1.02–1.03) - -
 log(LOS) > 2.5 0.96 (0.96–0.96) 0.96 (0.96–0.96) - -
Had provincial health insurance #
 Yes 0.96 (0.81–1.14) - 1.15 (0.63–2.10) -
 No 1.00   1.00  
Country of birth
 Canada 0.68 (0.55–0.83) - 0.80 (0.47–1.37) -
 Foreign, low-moderate incidence 0.88 (0.74–1.04)   0.57 (0.33–0.98)  
 Foreign, high incidence country 1.00   1.00  
Immigration, years since arrival
 Foreign-born, unknown arrival date 1.47 (1.13–1.91) - 0.57 (0.28–1.15) -
 15 or more years 1.11 (0.92–1.35)   0.70 (0.34–1.44)  
 3–14 years 1.50 (1.26–1.79)   0.85 (0.50–1.42)  
 0–2 years 1.42 (1.17–1.71)   1.15 (0.58–2.28)  
 Canadian-born 1.00   1.00  
Homeless   -   -
 Yes 0.89 (0.56–1.40)   0.26 (0.11–0.63)  
 No 1.00   1.00  
Cancer   -   
 Yes 0.82 (0.55–1.23)   1.42 (0.89–2.26) -
 No 1.00   1.00  
Diabetes   -   
 Yes 0.92 (0.76–1.11)   1.05 (0.63–1.75) -
 No 1.00   1.00  
HIV
 Positive 0.83 (0.70–0.99) 0.77 (0.66–0.90) 0.93 (0.59–1.47) 0.61 (0.40–0.91)
 Negative or unknown 1.00 1.00 1.00 1.00
Renal disease
 Yes 0.55 (0.43–0.70) 0.59 (0.46–0.75) 0.45 (0.21–0.95) 0.58 (0.31–1.10)
 No 1.00 1.00 1.00 1.00
Liver disease
 Yes 0.79 (0.66–0.94) - 1.62 (0.99–2.66) -
 No 1.00   1.00  
Ever substance abuse
 Yes 0.91 (0.79–1.05) - 0.88 (0.58–1.33) -
 No 1.00   1.00  
Number of co-morbidities
 2 or more 0.65 (0.56–0.75) - 0.74 (0.44–1.25) -
 1 0.85 (0.73–1.00)   0.69 (0.36–1.31)  
 0 1.00   1.00  
Ever smoker
 Yes 0.84 (0.74–0.96) - 0.91 (0.59–1.40) -
 No 1.00   1.00  
TB diagnosis
 Pulmonary, Smear+ 0.61 (0.51–0.72) 0.64 (0.54–0.77) 1.51 (0.84–2.69) 1.26 (0.78–1.99)
 Pulmonary, Smear- 089 (0.73–1.09) 1.02 (0.84–1.26) 1.50 (0.80–2.83) 1.81(1.07–3.04)
 Extra-pulmonary 1.00 1.00 1.00 1.00
Cavitary TB
 Yes 0.92 (0.90–1.05) - 1.91 (1.13–3.25) -
 No 1.00   1.00  
Miliary TB
 Yes 0.83 (0.63–1.10) - 1.13 (0.70–1.83) -
 No 1.00   1.00  
Any pulmonary TB-related symptoms
 Yes 0.65 (0.50–0.85) 0.70 (0.55–0.90) 0.61 (0.42–0.90) 0.46 (0.27–0.80)
 No 1.00 1.00 1.00 1.00
Any systemic TB-related symptoms
 Yes 0.80 (0.69–0.93) - 1.16 (0.60–2.26) -
 No 1.00   1.00  
Multidrug or poly-drug resistance
 Yes 0.65 (0.50–0.85) 0.44 (0.32–0.60) 0.62 (0.28–1.39) 0.28 (0.12–0.66)
 No 1.00 1.00 1.00 1.00
Teaching hospital
 Yes 0.86 (0.75–0.99) 0.81 (0.71–0.92) 0.99 (0.62–1.59) -
 No 1.00 1.00 1.00  
  1. IQR interquartile range, LOS length of stay, HR hazard ratio, CI confidence interval
  2. aModels adjusted for all reported variables
  3. bCox Proportional Hazard model is modeling the time to discharge; a hazard ratio of less than one indicates a longer LOS (ie. A HR for multidrug or poly-drug resistance = 0.45 can be interpreted as: the rate of discharge from hospital is 55% slower for patients with drug resistance compared to those without drug resistance)
  4. cGiven strong evidence that proportional hazards assumptions did not hold for age (lines crossed in the log-log plot), we included an interaction term in the model of age (continuous, in years) multiplied by the LOS. This interaction term indicates that the effect of age was not constant throughout the length of stay