Healthcare Case Studies

Estimating Health Care-Associated Infections and Deaths in U.S. Hospitals

-A CASE STUDY

Healthcare-associated infections (HAIs) cause good number of morbidities and mortalities in the United States and are among the most common adverse events in healthcare. So a study was conducted to find a national estimate of the number of healthcare-associated infections (HAI) and deaths in United States hospitals.

A multi-step approach and three data sources were used. In the study the main source of data was the National Nosocomial Infections Surveillance (NNIS) system, data from 1990–2002, conducted by the Centers for Disease Control and Prevention. The data from the (NHDS) National Hospital Discharge Survey (for 2002) and the American Hospital Association Survey (for 2000) were used to complement NNIS data. The percentage of patients with an HAI whose death was determined to be caused or associated with the HAI from NNIS data was used to estimate the number of deaths.

The estimation of HAIs was based on four sub-populations (newborns in high-risk nurseries, newborns in well-baby nurseries, adults and children in ICUs, and adults and children outside of ICUs) and five types of infections viz. surgical site infections, bloodstream infections, pneumonia, urinary tract infections, and other sites combined.

1. Estimate of HAI among newborns: The total infections were calculated by multiplying the number of NHDS patient-days by the corresponding NNIS infection rates for the high-risk nursery and well-baby nursery (number of patient-days × infection rate/patient-days = number of infections).

2. Estimate of HAI among adults and children in ICUs: For ICU patients, the HAI rates were evaluated by using NNIS ICU data for each major site of infection (number of patient-days × infection rate/patient-days = number of infections).

3. Estimate of HAIs among hospitalized adults and children outside of ICUs: The surgical site was chosen for our calculations because the number of surgical procedures is available for the U.S. population in the NHDS. The number of surgical procedures in the NHDS was multiplied by the surgical site infection rate from NNIS 2002 surveillance. Then in the next step, from this estimate subtracted the surgical site infections among newborns and among adults and children in ICUs, which caused the total number of such infections among hospitalized adults and children outside of ICUs, i.e., 244,385. 20% of all HAIs in NNIS hospital-wide surveillance were surgical site infections; thus, we used that percentage to estimate the number of infections for other body sites.

4. Adjustment to include federal hospitals: For the adjustment, an adjustment factor was calculated by which we multiplied the number of non-newborn patient-days and non-newborn infection estimates.We took the number of patient-days in federal hospitals (11.6 million) from the AHA survey of 2000, added the number of nonfederal hospital patient-days among adults and children (192.4 million) and divided the sum by the nonfederal hospital patient-days among adults and children (192.4 million). The result was 1.06, which we used as a multiplier of the number of adult and children NHDS patient-days and infection estimates. The multiplier increased the number of HAI by 6%.

5. Estimate of deaths: After causality determination, thedeaths in which the HAI caused or contributed to the death were referred to these as deaths associated with HAIs. With NNIS infection data from 1999 to 2003, the percentage of patients with an HAI who died and the percentage of those whose death was associated with their HAI were calculated. The calculated percentage was then multiplied within each of the four subpopulations by the estimate of patients with an HAI.

The estimated number of healthcare-associated infections in U.S. hospitals by subpopulation and major site of infection, United States, 2002 has been tabulated below:

In 2002, the estimated number of HAIs in U.S. hospitals, adjusted to include federal facilities, was approximately 1.7 million wherein the estimated deaths associated with HAIs in U.S. hospitals were 98,987.The main cause was pneumonia followed by bloodstream infections, urinary tract infections, surgical site infections and infections of other sites.

In conclusion it can be said that HAIs in hospitals are an important cause of morbidity and mortality in the United States. The method described for estimating the number of HAIs was based on the prevailing data at the national level. However, the result shows the greater amount of effort is needed to minimize the burden of nosocomial infections. The preventive measures should be reinforced and surveillance measures should be heightened to prevent these Healthcare-associated infections (HAIs) which have turned into a great public health burden.