Calculating Peritonitis Rates: An Example
XYZ Dialysis Center has the following 1st quarter patient census:
| January 1–January 31 | 20 patients = 20 pt x 31 days = 620 patient days for January |
| February 1–February 28 | 20 patients = 20 pt x 28 days = 560 patient days |
| February 5–February 28 | 1 new patient started PD 2/5 = 1 pt x 24 days = 24 patient days |
| February 10–February 28 | 2 new patients started PD 2/10 = 2 pts x 19 days = 38 patient days |
| 560 + 24 + 38 = 622 patient days for February | |
| March 1–March 31 | 23 patients = 23 pt x 31 days = 713 patient days |
| March 12–March 31 | 2 new patients started 3/12 = 2 pt x 20 days = 40 patient days |
| March 21–March 31 | 2 new patients started 3/21 = 2 pt x 11 days = 22 patient days |
| 713 + 40 + 22 = 775 patient days for March |
Total patient days for 1st quarter: 620 + 622 + 775 = 2017 pt days at risk
Total number of peritonitis episodes during 1st quarter: 2
To calculate peritonitis rates in episodes per patient month:
Take patient days at risk, 2017 ÷ 30.4 (days per month: comes from 365 days/12 months) = 66.34 patient months experience
Take patient months experience, 66.34 ÷ 2 (number of peritonitis episodes) = 33.17
So the peritonitis rate for the first quarter is: 1 episode every 33.17 patient months
To calculate peritonitis rate in episodes per patient year:
Take patient days at risk, 2017 ÷ 365 (days per year) = 5.52 patient years experience
Take the number of peritonitis episodes, 2 ÷ 5.52 (patient years experience) = 0.36
So the peritonitis rate for 1st quarter is: 0.36 episodes per patient year
References used in this Appendix section
- Li PK, Szeto CC, Piraino B, Bernardini J, et al. Peritoneal dialysis-related infections recommendations: 2010 update. Perit Dial Int 2010; 30(4):393-423.
- Li PK, Szeto, CC, Piraino, B, et al. ISPD peritonitis recommendations: 2016 update on prevention and treatment. Perit Dial Int 2016; 36:481-508.