Situation: The infection prevention and control committee reports that the catheter-associated urinary tract infection (CAUTI) rate on a 32-bed adult surgical ward has been above the hospital target for two quarters. The head nurse forms an improvement team of staff nurses, a urologist, and an infection control nurse. The team introduces a nurse-driven catheter removal protocol in April. Its data are: January–March: 6 CAUTIs; 1,200 catheter-days; 2,700 patient-days June–August: 3 CAUTIs; 500 catheter-days; 2,650 patient-days Which conclusion do the data BEST support?

Before: 6 ÷ 1,200 × 1,000 = 5.0 CAUTIs per 1,000 catheter-days; after: 3 ÷ 500 × 1,000 = 6.0. Catheter-days fell from 1,200 to 500 while patient-days stayed nearly the same, so the protocol halved infections by reducing catheter use, but the risk for each catheter-day did not improve. The next cycle should target maintenance care (for example, bundle compliance) rather than abandon the removal protocol.

Interpretation of the data

The first step is to calculate the CAUTI rate per 1,000 catheter-days for each period. Before the protocol, 6 infections occurred over 1,200 catheter-days, giving a rate of 5.0 per 1,000 catheter-days. After implementation, 3 infections occurred over 500 catheter-days, giving a rate of 6.0 per 1,000 catheter-days. The rate per catheter-day actually increased slightly, which rules out option 3.

The total number of infections fell from 6 to 3, but this was driven almost entirely by a reduction in catheter exposure, not by safer care while the catheter was in place. Catheter-days dropped from 1,200 to 500, a 58% reduction, while patient-days remained essentially stable (2,700 vs. 2,650). This means the ward did not simply have fewer patients; it had fewer patients with catheters, or catheters were removed sooner.

Why the protocol still worked

A nurse-driven removal protocol reduces CAUTI primarily by shortening the duration of catheterization. Each day a catheter remains in place adds incremental risk for biofilm formation and ascending infection. The evidence supports this mechanism: nurse-directed removal protocols decrease catheter utilization and, through that pathway, reduce total CAUTI counts ^[1][2]. The reduction in catheter-days from 1,200 to 500 is the key process improvement.

Key point! CAUTI prevention has two distinct levers: removing unnecessary catheters (reduces exposure) and maintaining catheters properly while they are in place (reduces risk per day). The data show the first lever worked; the second did not improve.

What the unchanged per-day risk means

The per-day rate rising from 5.0 to 6.0 does not mean the protocol caused harm. It means the remaining catheter-days were concentrated among patients who genuinely needed catheterization and may have had higher baseline risk. However, it also signals that maintenance practices—such as meatal care, securement, drainage system integrity, and daily review of continued need—were not optimized during this cycle.

Watch out! Do not interpret a stable or slightly higher per-day rate as protocol failure. The appropriate conclusion is that the removal protocol successfully reduced exposure, and the next improvement cycle should target maintenance bundle compliance .

Comparison of the two periods

Measure	January–March	June–August	Interpretation
Total CAUTIs	6	3	Halved in absolute terms
Catheter-days	1,200	500	58% reduction in exposure
Patient-days	2,700	2,650	Admissions essentially unchanged
CAUTI per 1,000 catheter-days	5.0	6.0	Per-day risk did not fall

The stability of patient-days directly refutes option 2. The ward did not experience a meaningful decline in patient volume; the change was in how many of those patients had indwelling catheters and for how long.

Clinical and exam relevance

For licensure exams, CAUTI questions often test the distinction between device utilization ratio and infection rate per device-day. A nurse-driven removal protocol improves the former but may not change the latter. When a quality improvement question presents both catheter-days and patient-days, calculate both the absolute infection count and the rate per catheter-day before drawing conclusions.

The correct interpretation is that fewer catheter-days reduced the total number of infections, while the risk per individual catheter-day remained essentially unchanged. This supports continuing the removal protocol and adding a maintenance care bundle as the next intervention.