Dan Bronson-Lowe, PhD, CIC Senior Clinical Manager Baxter Healthcare Corporation No conflicts of interest to disclose.
Clinic A Clinic B 20 vaccinated 5 vaccinated 100 total 5 total 20% vaccinated 100% vaccinated
Counts Ratios Proportions Rates Numerator Denominator x 10n Where: 10 0 = 1 10 1 = 10 10 2 = 100 10 3 = 1,000 10 4 = 10,000 and so on
Number or rate of events/items/persons/etc. in group 1 Number or rate of events/items/persons/etc. in group 2 x 10 n A hospital with 420 inpatient beds has 3 IPs. 420 / 3 (x 1) = 140 inpatient beds per IP Ratio of inpatient beds to IPs is 140:1.
Number of events/persons with a particular characteristic Total number of events/persons (of which the numerator is a subset) x 10 n During 2015 a hospital had 50 CAUTIs, of which 18 were in male patients. 18 / 50 (x 100) = 36 CAUTIs in males per 100 CAUTIs = 36% of CAUTIs were in males
Number or rate of events during the time period Number or rate of events/items/persons/etc. at risk during the time period x 10 n A hospital with 80,000 admissions in 2014 had 120 cases of healthcare-acquired C. difficile infections in 2014. 120 / 80,000 (x 1) = 0.0015 infection per admission per year 120 / 80,000 (x 10,000) = 15 infections per 10,000 admissions per year
1. Is it based on (Numerator/Denominator) x 10 n? No = Not a Ratio. Stop here. Yes = Ratio. Go to Question 2. Example A 24 patients Example B (Ratio) 16 males / 8 females = 2 males per female Example C 16 males/24 patients (x100) = 67% Example D (Ratio) 8 patients per day
2. Is the Numerator a subset of the Denominator? No = Not a Proportion. Go to Question 3. Yes = Proportion. Go to Question 3. Example B 16 males / 8 females = 2 males per female Example C 16 males/24 patients (x100) = 67% Example D 8 patients per day
3. Is time part of the Denominator? No = Not a Rate. Stop here. Yes = Rate. Stop here. Example B 16 males / 8 females = 2 males per female Example C 16 males/24 patients (x100) = 67% Example D 8 patients per day
Incidence Mortality or Cure Prevalence
Prevalence = Number of existing cases at a given point in time Total population at a given point in time Point Prevalence Specific point in time Period Prevalence Specific period in time
Prevalence = Number of isolation patients on Unit W on June 4th Total population on Unit W on June 4th
Patients on Isolation on Unit W - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Patient Presence on Unit W - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Prevalence = Number of isolation patients on Unit W on June 4th Total population on Unit W on June 4th Prevalence = 5 isolation patients 7 patients total = 0.71 71%
Prevalence = Number of isolation patients on Unit W in June Total population on Unit W in June
Patients on Isolation on Unit W - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Patient Presence on Unit W - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Prevalence = Number of isolation patients on Unit W in June Total population on Unit W in June Prevalence = 8 isolation patients 12 patients total = 0.67 67%
Incidence = Number of new cases during a given time period Total at-risk population (or time) observed Incidence Proportion Cumulative Incidence Person-based; uses people at risk Incidence Rate Incidence Density Time-based; uses time at risk
Incidence Proportion = Number of new cases during a given time period Total at-risk population observed
CAUTI Events on Unit Z - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Patient A B C D E F G H I J K L Foley Patient Catheter Presence Use on Unit Z -- June 2015 1 7 14 21 28 Day of the Month
Incidence Proportion = Incidence Proportion = Number of new cases during a given time period Total at-risk population observed 3 new CAUTIs in June 12 patients in June = 0.25 25%
Incidence Proportion = Incidence Proportion = Number of new cases during a given time period Total at-risk population observed 3 new CAUTIs in June 9 patients with urinary catheters in June = 0.34 34%
Foley Catheter Use on Unit Z - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Incidence Rate = Number of new cases during a given time period Total at-risk time observed
CAUTI Events on Unit Z - June 2015 Patient A B C D E F G H I J K L 1 7 14 21 28 Day of the Month
Patient A B C D E F G H I J K L Foley Catheter Use on Unit Z - June 2015 1 7 14 21 28 Day of the Month Catheter- Days 11 0 4 7 30 6 0 0 14 30 3 9 114
Incidence Rate = Number of new cases during a given time period Total at-risk time observed Incidence Rate = 3 new CAUTIs in June 114 urinary catheter-days in June = 0.026 CAUTIs per catheter-day = 26 CAUTIs per 1000 catheter-days
Attack Rate = Number of new cases during a given time period Total at-risk population observed Overall Attack Rate = 8 new cases of norovirus this week 420 in-patients = 0.02 2%
Attack Rate = Number of new cases during a given time period Total at-risk population observed Food-Specific Attack = Rate 7 new cases of norovirus this week (ate salad) 120 in-patients (ate salad) = 0.06 6%
Mortality Rate = Number of deaths Total at-risk population observed x10 n (per year) Crude Mortality Rate = 100 deaths 20,000 total population x1,000 (per year) = 5 deaths per 1,000 population per year
Mortality Rate = Number of deaths Total at-risk population observed x10 n (per year) Cause-Specific Mortality = Rate 2 tuberculosis deaths 20,000 total population x100,000 (per year) = 10 TB deaths per 100,000 population per year
Hospital A Hospital B 25 CAUTIs 11 CAUTIs 8000 catheter-days 8000 catheter-days 3.1 CAUTIs per 1,000 catheter-days 1.4 CAUTIs per 1,000 catheter-days
Hospital A Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 24 6000 4.0 Rehab 1 2000 0.5 Total 25 8000 3.1 Hospital B Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 8 2000 4.0 Rehab 3 6000 0.5 Total 11 8000 1.4
Hospital A Hospital B Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days ICU 12 6000 2.0 Medical 3 1000 3.0 Oncology 3 1500 2.0 Ortho 0 750 0.0 Rehab 1 2000 0.5 Stepdown 3 1500 2.0 Surgical 18 3000 6.0 Telemetry 0 250 0.0 Total 40 16000 2.5 Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days ICU 2 200 10.0 Medical 3 3000 1.0 Oncology 10 2500 4.0 Ortho 1 450 2.2 Rehab 0 1200 0.0 Stepdown 0 50 0.0 Surgical 10 15000 0.7 Telemetry 1 80 12.5 Total 27 22480 1.2
Direct Standardization Your Population Category-Specific Rates Standard Population Indirect Standardization Your Population Category-Specific Rates Standard Population
Hospital A Direct Standardization Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 24 6000 4.0 Rehab 1 2000 0.5 Total 25 8000 3.1 Standard Hospital Unit Number of CAUTIs Number of Catheter-Days Medical 4000 Rehab 4000 Total 8000 CAUTI rate per 1,000 catheter-days
Hospital B Direct Standardization Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 8 2000 4.0 Rehab 3 6000 0.5 Total 11 8000 1.4 Standard Hospital Unit Number of CAUTIs Number of Catheter-Days Medical 4000 Rehab 4000 Total 8000 CAUTI rate per 1,000 catheter-days
Hospital A Hospital B 25 CAUTIs 11 CAUTIs 8000 catheter-days 8000 catheter-days Crude Rate: 3.1 CAUTIs per 1,000 catheter-days Unit-Standardized Rate: 2.3 CAUTIs per 1,000 catheter-days Crude Rate: 1.4 CAUTIs per 1,000 catheter-days Unit-Standardized Rate: 2.3 CAUTIs per 1,000 catheter-days
Hospital A (Standardized) Indirect Standardization Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 24 6000 4.0 Rehab 1 2000 0.5 Total 25 8000 3.1 Hospital B (Standard Population) Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 8 2000 4.0 Rehab 3 6000 0.5 Total 11 8000 1.4
Hospital A (Expected) Indirect Standardization Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 24 6000 4.0 Rehab 1 2000 0.5 Total 25 8000 3.1 Hospital A (Observed) Unit Number of CAUTIs Number of Catheter-Days CAUTI rate per 1,000 catheter-days Medical 24 6000 4.0 Rehab 1 2000 0.5 Total 25 8000 3.1
SIR = Observed number of infections Expected number of infections Better Same Worse 0 1 2 SIR
Crude Rates Standardized Rates Category-Specific Rates
It is a truth universally acknowledged, that an infection preventionist in possession of a good dataset must be in want of an interpretation.
Sensitivity 100% Specificity 100% No HAI HAI 0 1 2 3 4 5 6
Disease No Disease Positive Test True Positive False Positive Total Positives Negative Test False Negative True Negative Total Negatives Total Diseased Total Disease-Free Total Population Number of True Positives Sensitivity = (x 100) Total Number of Diseased
Disease No Disease Positive Test True Positive False Positive Total Positives Negative Test False Negative True Negative Total Negatives Total Diseased Total Disease-Free Total Population Number of True Negatives Specificity = (x 100) Total Number Disease-Free
Disease No Disease Positive Test True Positive False Positive Total Positives Negative Test False Negative True Negative Total Negatives Total Diseased Total Disease-Free Total Population Number of True Positives PPV = (x 100) Total Number with Positive Tests
Disease No Disease Positive Test True Positive False Positive Total Positives Negative Test False Negative True Negative Total Negatives Total Diseased Total Disease-Free Total Population Number of True Negatives NPV = (x 100) Total Number with Negative Tests
Sensitivity: 80% Specificity: 91% Positive predictive value: 85% Negative predictive value: 87%
PPV = 8% PPV = 85%
NPV = 99% NPV = 87%