Improving peritoneal dialysis fluid culture-positivity yield from 2022 to 2023

Microbiological testing of peritoneal dialysis bags for peritonitis often yields culture-negative results. Culture-negative samples should not exceed > 15% according to the International Society for Peritoneal Dialysis. To reduce this issue, the addition of a blood culture bottle incubation step to the culture process was introduced at the Infection Control Services Laboratory (ICSL) of the National Health Laboratory Services (NHLS).

The aim of the study was to ascertain if the change in methodology increased the culture-positivity yield and reduced the culture-negative percentage.

Data from the NHLS Central Data Warehouse (CDW) were analysed to compare the culture-positive results over two periods: June-December 2022 when the non-blood culture (B/C) bottle method was used and January-July 2023 when the B/C bottle method was implemented.

The non-B/C culture method yielded a 23% culture-positivity yield, whereas the B/C bottle-based method yielded a 51% culture-positivity yield. However, the culture-negative yield for the B/C bottle-based method was high at 49%.

The change in dialysis bag processing in 2023 led to a more than doubling in culture-positivity yield. However, the culture-negative percentage remained high. As a result, further modifications to the methodology are needed.

The study findings illustrate that the addition of the B/C bottle incubation step significantly improved peritoneal dialysis bag culture yields which directly impacts patient management.