White particulate matter: report of the ad hoc industry review group

What´s floating on my plasma?

We report on a preanalytical issue we encountered during routine clinical chemistry analyses, potentially leading to deviated analysis results and believe that it might help other laboratories to overcome similar problems. In a heparin-gel tube we measured an implausible glucose value of 0.06 mmol/L. Re-measurement of the same sample resulted in a glucose value of 5.4 mmol/L. After excluding an analytical error, we inspected the sample closer and found a white material as well as fatty droplets floating on the surface of the plasma tube. Evaluation of these structures revealed that the white particulate matter (WPM) consisted of fibrinogen, platelets and leukocytes and the fatty droplets most probably originated from the separator gel. We concluded that these structures formed a temporary clot in the instruments pipetting needle thereby altering the sampling volume and subsequently the measured glucose value. The formation of WPM might be attributable to high speed centrifugation, high cholesterol levels, the gel formulation or a combination of several issues such as temperature, heparin concentration, pH and patient-specific factors. The gel droplets were most probably caused by an aberrant gel formulation in combination with an improper storage of the empty tubes on the wards prior to phlebotomy. After adding an additional instrument cleansing cycle and changing to another batch of heparin tubes the problems could be significantly reduced.

Factors affecting the formation of white particulate matter in red blood cell components

BACKGROUND

Recently white particulate matter (WPM) in red blood cell (RBC) components has received increased attention. The nature and causes of WPM formation were investigated.

STUDY DESIGN AND METHODS

Whole-blood units were collected from 18 healthy subjects with three different types of collection sets. Six units were collected into each type. Units were divided into four equal parts and stored for 4 hours: two parts at room temperature and two at 4 degrees C. RBCs were prepared from each quarter-unit: two by heavy centrifugation (5000 x g) and two by light centrifugation (2000 x g). Whole blood was inspected for WPM over 4 hours and RBCs over 1 hour.

RESULTS

No WPM was detected in whole blood, but WPM was detected in at least one RBC component from 9 of the 18 donations. The 36 components prepared by heavy centrifugation were more likely to contain WPM than the 36 prepared by light centrifugation (50% vs. 19%; p < 0.02). The incidence of WPM was similar among RBCs stored at room temperature and 4 degrees C. Donors of RBCs with WPM had higher total cholesterol levels than donors of components without WPM (191 +/- 20 mg/dL vs. 163 +/- 32 mg/dL; p < 0.04), but there was no difference in triglyceride levels between the two groups.

CONCLUSIONS

WPM is an expected consequence of standard RBC manufacturing methods, but it is more frequent in RBCs prepared by heavy centrifugation and from donors with higher cholesterol levels.