Using pH paper to QC platelets

An e-Network member reports that her blood bank collects platelets from volunteer blood donors and that her center performs QC on platelet products each month. However, much to the dismay of the inquiring blood banker, her facility's pH meter has NOT functioned properly for the last few weeks, and her center personnel substituted using pH paper for a broken pH meter without informing the center medical director! The center's medical director recently discovered this situation and wants to know if other e-network members use pH paper for QC of platelet products. If so, how does one validate that pH paper is working properly for testing the pH of platelet products intended for transfusion? Should the inquiring blood collection center recall all of the platelet products that were distributed during the time that platelet product QC was based on pH paper reactions? The following reply was submitted in response to the above situation.

1. A blood bank physician on the East Coast responded that her facility would not use pH paper for QC of platelets. According to the East Coast blood banker, pH paper is not able to be calibrated due to its subjectivity based on color perception. The responding blood banker adds that in her opinion, the main problem with the center using pH paper is the use of this testing without the responsible person's knowledge and approval, namely the medical director. The East Coast blood banker thinks that recall of all platelet products that were collected during the time period involved is appropriate. In addition, this blood banker feels that the medical director of the inquiring facility needs to address staff in the laboratory to ensure that this type of incident does not recur.

ADDENDA Mar. 7, 2002

2. A blood banker who used to work in a hospital transfusion service believes that if the pH paper was tested against pH calibration standards with acceptable results and was not expired, he fails to see a problem using it as a backup for a pH meter. While working at the hospital (until Feb 2000) he reports that they used pH paper instead of a meter with good results. As a medical technologist (Clincal Laboratory Scientist in current vernacular), he states that he is trained to make judgement calls, particularly in Transfusion Medicine. He and other med techs used pH standards to validate pH paper. He adds that it is important to choose a pH paper with ranges within the scope of expected results. Kits are available with an array of short and wide ranges that measure tenths of a pH unit over the entire pH range. The hospital where he used to work may be using a meter now, but a few years back the pH paper was quite satisfactory. A pH meter was available in the Chemistry Department, but few blood bank techs had experience with it. He concludes that it would be a good idea to verify the results of the pH paper against a meter for validation of the process if it was to be used as a primary or backup measurement.
   
   Editor's note: The responding ex-hospital blood banker does not address the problem of the staff at the inquiring blood banker's facility implementing the use of pH paper for platelet QC in place of a broken pH meter without first validating that the pH paper works in that QC setting and without first obtaining approval from the medical director of the blood establishment.

ADDENDA Mar. 11, 2002

3. A blood banker from the state of Washington states that his facility looked into pH paper for platelet QC a few years back. They were told by several people who should know such things that pH paper could not be reliably used with a protein-based fluid like plasma. The Washington blood banker believes it makes intuitive sense that the use of a saline based buffer as a "calibrator" for pH paper does not mean it would work equally well in the presence of high concentrations of protein. Based on this information, his facility bought a very simple pH meter "stick" from Hanna instruments and have been very happy with its performance.

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Ira A. Shulman, MD
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W. Tait Stevens, MD
CBBS e-Network Forum Editor & Moderator

Elizabeth M. St. Lezin, MD
CBBS e-Network Forum Associate Editor & Moderator