Ecologic evaluation of central line associated bloodstream infection (CLABSI) and secondary BSI rates for case misclassification in Pennsylvania

Background: Declines in National Healthcare Safety Network (NHSN) defined central line associated bloodstream infection (CLABSI) incidence rates have been increasingly reported. However, public reporting of healthcare-associated infection (HAI) rates has raised questions regarding data validity, specifically systematic  and intentional misclassification of CLABSIs as secondary BSIs (sBSI).

Objective: To look for evidence of CLABSI misclassification by comparing CLABSI and sBSI rates in Pennsylvania (PA) hospitals during 2 full years of PA’s state-mandated reporting of all HAIs to NHSN.  

Methods: We compared the change in the CLABSI incidence rate per 1000 central line days (CLD) and sBSI incidence rate per 1000 patient days (PD) over two 1-year periods (1: July 08-June09 and 2: July 09-June10) for locations in PA hospitals that reported data to NHSN throughout the two-year period and had ≥100 CLD/year. Differences in the median (Median scores test) and the distribution (Kuiper test) of CLABSI and sBSI rates for each year assessed. P-values of <0.05 were considered significant.  To test if decreases in CLABSI correlated with increases in sBSI, the correlation between the change in CLABSI and sBSI rate from year 1 to year 2 for each location was calculated using Spearman’s Rank Correlation Coefficient.

 Results: A total of 939 locations from 186 hospitals reported data for all 24 months and had ≥100 CLD/year. The median CLABSI rate decreased from year 1 (0.635 per 1000 CLD) to year 2 (0.000 per 1000 CLD) (p<0.0001), and a significant change in the distribution of CLABSI rates between the two years occurred (p=0.0004). The median sBSI rate remained stable from year 1 (0.100 per 1000 PD) to year 2 (0.096 per 1000 PD p=0.8176), and there was no change in the distribution of these two rates (p=0.9986). There was no correlation (r=-0.0243, p=0.4578) in the change of the CLABSI and sBSI rates between year 1 and 2.

Conclusions:  Mandatory reporting of comprehensive HAI data from PA hospitals beginning in 2008 provided a unique opportunity to evaluate both CLABSI and sBSI rates.  We found no evidence of an increase in sBSIs to suggest that the concurrent significant decrease in CLABSI may have been due in part to misclassification of CLABSIs as sBSIs. These results suggest that intentional case misclassification (and reporting events as sBSI) is not widespread. Additional data validation efforts are needed to generalize these findings and to further evaluate the degree of case misclassification.