Platelet Component False Positive Detection Rate in Aerobic and Anaerobic Primary Culture: A Systematic Review and Meta-Analysis

Platelet Pathogen Reduction Technology-Should We Stay or Should We Go…?

The recent COVID-19 pandemic has significantly challenged blood transfusion services (BTS) for providing blood products and for keeping blood supplies available. The possibility that a similar pandemic event may occur again has induced researchers and transfusionists to investigate the adoption of new tools to prevent and reduce these risks. Similarly, increased donor travelling and globalization, with consequent donor deferral and donor pool reduction, have contributed to raising awareness on this topic. Although recent studies have validated the use of pathogen reduction technology (PRT) for the control of transfusion-transmitted infections (TTI) this method is not a standard of care despite increasing adoption. We present a critical commentary on the role of PRT for platelets and on associated problems for blood transfusion services (BTS). The balance of the cost effectiveness of adopting PRT is also discussed.

Increased frequency of false-positive bacterial detection after implementation of new guidelines for large-volume delayed sampling of platelets

BACKGROUND

The updated guidance for improving bacterial detection (BD) of platelets has included the implementation of large-volume delayed sampling (LVDS) with the addition of anaerobic culture bottles (BPNs) and sampling of each platelet split product.

METHODS

The frequency of BD was reviewed during this LVDS time period in comparison with pre-LVDS and the Post-Approval Surveillance Study of Platelet Outcomes, Release Tested (PASSPORT) study (when BPNs were last used).

RESULTS

There was more than a twofold increase in bottles inoculated per collection during LVDS, with an almost fivefold increase in sample volume collected. During LVDS, the concordance of split products within an initial reactive collection was only 8.7%. There was no difference in LVDS aerobic culture bottle (BPA) true positives (TPs), but there was a significant increase in LVDS false positives (FPs), p < .0001, compared to both PASSPORT and pre-LVDS, respectively. There was an increase in BPN TPs during LVDS (p < .05 compared to PASSPORT), with predominance of Cutibacter acnes (C. acnes), noted exclusively in BPN, and accounting for more than two-fifths of all organisms detected. Time to alarm during LVDS for TPs had two peaks with one due to C. acnes at 96 h compared to 17 h for non-C. acnes.

DISCUSSION

The high FP frequency, along with low clinical significance of TPs found in BPNs, has led to the needless discard of inventory, as the utility of BPNs in BD for platelets is yet to be established and may require much larger studies.

Characteristics of False-Positive Alarms in the BacT/Alert 3D System

The BacT/Alert system has been used for detecting the presence of bacteria in various clinical settings as well as in blood services, but it is associated with a relatively high incidence of false-positive results. We analyzed the results of our quality control sterility testing of blood products by BacT/Alert 3D to understand the mechanism of false-positive results. Anaerobic and aerobic bottles were inoculated with 10 mL of samples and cultured in BacT/Alert 3D for 10 days. Positive-reaction cases were classified as true positive if any bacterium was identified or false positive if the identification test had a negative result. The detection algorithm and the bottle graph pattern of the positive reaction cases were investigated. Among the 43,374 samples, 25 true positives (0.06%) and 29 false positives (0.07%) were observed. Although the detection algorithm of all true positives and 25 of 29 false positives was accelerating production of CO2, a steep rise in the bottle graph was observed only in the true positives, and it was not observed in either of the false positives. Four of 29 false positives were dependent on high baseline scatter reflections. Furthermore, evaluating the bottle graph pattern of Streptococcus pneumoniae, a bacterium known to autolyze, we confirmed that no viable bacterium was detected even if a steep rise was observed. In conclusion, the bottle graph pattern of positive reactions allows the differentiation between true positives and false positives. In case of a steep rise without bacterium detection, the bacterium might have autolyzed. Moreover, positive reactions with high baseline scatter reflections, despite immediate loading of bottles after sampling, are potentially false positive. IMPORTANCE In clinical settings, false-positive results are treated as positive until bacterial identification. It may result in the discarding of blood products in blood centers or affect clinical decisions in hospitals or testing facilities. Moreover, the management of these samples is usually time- and labor-consuming. The results of our study may help clinicians and laboratory staff in making a more precise evaluation of positive reactions in BacT/Alert.