The following question was sent to the e-network for discussion: Our blood center uses copper sulfate for our hemoglobin screening to determine donor eligibility. Our SOP currently requires us to QC our copper sulfate daily and that the specific gravity must be 1.053 +/- .0005. We never know from day to day whether or not our copper sulfate will QC within the above parameters (often ours QC at 1.052 which is unacceptable - we do spun hematocrits for the day if the copper sulfate doesn't QC). Do other blood centers have this problem? What are their QC protocols when using copper sulfate? Does anyone have any suggestions that may enlighten us as to why this may be happening?

To which the following replies were received:

1. The unacceptable QC may be due to varying temperatures between the hydrometer and the copper sulfate solution. You may want to allow some time for the hydrometer and the solution to come to equal temperature before you measure the specific gravity.

2. We also use copper sulfate for hemoglobin screening. We have a certified hydrometer to use for QC. However if you check certification it give a specific gravity at a designated temperature. If the temperature of the copper sulfate or area in which it is stored, then a correction factor must be calculated to determine the CuSO4 specific gravity at that temperature. Additionally if the CuS04 had been opened and allowed to evaporate, the specific gravity of the solution can change. This change in specific gravity can be undetectable at first, but over time the change can be more significant.

3. We have found that because copper sulfate is temperature-sensitive that minor temperature variations affect the specific gravity. To monitor the range of "room temperature" we have installed min/max thermometers proximal to the storage areas. We carefully selected the storage areas based on the performance history of the solution. We have had no further problems.

4. The copper sulfate measurements done at our facility are done in the laboratory - once for each lot number shipped to us. I am reminded that this is not an easy task - and that there is a correction factor for temperature. But mostly I am reminded that the second way of verifying your copper sulfate - according to an older version of the technical manual, is to drop specimens with known hemoglobin values around the 12.5 gm/dl level and see what floats and what doesn't! Qualifying copper sulfate prior to use requires an extremely sensitive method that is very dependent on measurement equipment.

5. We do QC upon receipt only and have not had any problems. We do monitor its storage temperature. The FDA has been satisfied with that.

6. Having evaluated the CuS04 we use we can say the following: As the CuS04 gets cooler the specific gravity tends to be higher, and as the CuS04 gets warmer the specific gravity gets lower. We constantly receive bottles of CuS04 having too high of a specific gravity. Through investigation we have found that the solution has been stored in a cool location and had not warmed sufficiently. When warmed to around 75 F almost every bottle has passed. We do know that the testing for CuS04 completed in the factories is at 77 F, and it is checked by weight and not specific gravity. We check it at room temperature (if it is allowed to warm to that) which tends to be around 70 - 72 F and we use a hydrometer. Hydrometers on the other hand are tested at 60 F. This means that at 60 F the hydrometer will accurately read a solution at 60 F. A table of correction has been made for Hydrometers, however converting it for usage would require measuring the temperature as well as the specific gravity and then adjusting. Corrective actions: When staff cannot QC the CuS04 we ask them if they mixed it well, has it been sitting at room temperature and for how long, is the hydrometer also sitting at room temperature, is the hydrometer clean. If the staff still cannot QC it they send it to be evaluated. Once it is received, we let it sit at around 72 - 74 F and evaluate the solution. If it can be QC'd within range it is marked with the results and returned. If not, then it is not used. Occurrence rate in the summer is not very often, maybe once every other month. During the winter the incidence is higher maybe 1-2 times a month. With the exception of one or two bottles we have always been able to get it QC'd.

7. Why do they care if the copper sulfate is more concentrated, e.g., 1.052? This would reject more donors who would, or should, have passed. Thus, they would improve the potency and efficacy of their whole blood or RBC units. Unless 1.0535 would permit someone with a hemoglobin of less than 12.5 g/dL (or more correctly less than 12.0 since 12.5 is + or - 0.5 g/dL) to donate, that level is too restrictive too. We were cited by the FDA several years ago for failing to recap the copper sulfate bottles in between donors, ostensibly because of some risk, which I tried to explain would only be evaporation of water and concentration of the solution. I argued that a more concentrated solution would not adversely impact the safety, purity, potency, or efficacy of our rbcs, but might improve potency and efficacy. We were cited nonetheless and had to agree to recap the bottles in between donors!

8. CuSO4 is QC'd daily in Mobile Staging then a minimum of 30ccs is dispensed in small containers for the mobiles. Each container is labeled as CuSO4, lot #, date, employee's initials and specific gravity. We also require that the specific gravity QCs at 1.053 +/- .0005. We avoid performing the QC at drives and on donor coaches under changing conditions and/or temperatures? The only time our QC fell outside acceptable parameters, it was due to a broken hydrometer.

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