Method-specific and unexplained reactivity in automated solid-phase testing and their association with specific antibodies.

CONCLUSIONS: The inherent tradeoff between sensitivity and specificity in the detection of unexplained antibodies has been the objective of many studies, editorials, and journal articles. Many publications note that no method is capable of detecting all clinically significant antibodies while avoiding all clinically insignificant antibodies. This study describes the frequency of nonspecific reactivity and unexplained reactivity in solid-phase testing, along with the subsequent development of specific antibodies (Abs). In this study, nonspecific reactivity (NS) is defined as method-specific panreactivity detected by solid-phase testing only, with no reactivity in other methods. Unexplained reactivity (UR) is defined as reactivity present and detectable in all test methods after all clinically significant antibodies were ruled out following a standard antibody identification algorithm using selected cell panels. This retrospective study evaluated antibody detection tests of patients at a single center for 2 years using two automated solid-phase instruments that used the same three-cell antibody detection test. Antibody identification was performed with solid-phase panels supplemented with a polyethylene glycol tube method as needed. Of the 1934 (5%) samples with a positive antibody detection test, 29 had unavailable work-up data, leaving 1905 (98.5%) samples eligible for inclusion in the study. The data revealed the following: Ab only 999 (52.4%); UR only 429 (22.5%); Ab and UR 227 (11.9%); NS only 206 (10.8%); Ab and NS 24 (1.3%); UR and NS 14 (0.7%); and Ab, UR, and NS 6 (0.3%). Patients with a positive follow-up antibody detection test had UR and NS replaced with a specific Ab in 23 of 656 UR (3%) and 8 of 230 NS (3%) cases, respectively. Additionally, six patients with UR developed a specific Ab along with persistent UR, and no patients with persistent NS developed a specific Ab. The study concluded that both UR and NS can be encountered in solid-phase testing, and both UR and NS can persist in follow-up testing. Specific Ab was observed to replace UR in a few patients.

Safety of a liberal policy for extended-date preadmission testing samples.

BACKGROUND: Regulations governing pretransfusion testing allow specimen expiration to be extended past 3 days before the transfusion if a patient has not been transfused or pregnant in the preceding 3 months. Our hospital allows extension of the expiration of a presurgical specimen to 28 days if 1) the patient has neither been transfused nor pregnant in the past 3 months, 2) the patient does not have an antibody history, and 3) the current antibody screen (ABSC) is negative. Patients not meeting Criteria 2 and 3 are required to have specimens redrawn on the day of surgery (DOS). We evaluated the necessity of this policy. STUDY DESIGN AND METHODS: From October 2009 to September 2010, there were 132 patients who did not meet the above criteria for specimen extension. Equivalent tests were performed on preadmission testing (PAT) and DOS specimens, and the results were compared. RESULTS: The majority (113, 86%) of the samples redrawn on the DOS showed no change in antibody serology upon reinvestigation. Of the remaining patients, DOS specimens did not identify any new antibodies or change in blood product choices. CONCLUSION: Of the PAT specimens rejected for antibody history or positive ABSC, none had new significant serologic findings on DOS. Based on these results, requiring a repeat specimen on the DOS may not be clinically necessary. Our facility changed the PAT policy to extend specimen acceptability to patients with red blood cell antibody history or positive ABSC at time of PAT. A 6-month follow-up period showed that this practice is safe.

Establishing an antigen-negative red blood cell inventory in a hospital-based blood bank.

BACKGROUND: Our blood bank is part of a large academic institution with an active sickle cell anemia program. We provide sickle patients with blood phenotypically matched for C/c, E/e, and K antigens. Since licensed reagents are available for phenotyping C/c, E/e, and K on an automated blood analyzer, we decided to evaluate whether establishing our own inventory of blood negative for those antigens would result in cost savings and decreased turnaround time (TAT). STUDY DESIGN AND METHODS: Antigen typing of blood units for C/c, E/e, and K was validated. From March 1, 2012, to August 31, 2012, a total of 1033 units from our own donor center and from our suppliers were phenotyped. We compared direct cost savings and TAT for blood availability with historical data before we began phenotyping. RESULTS: Thirty-eight percent of typed antigen-negative (AG-) units were transfused to sickle patients. An additional 35% were transfused to nonsickle patients needing AG- blood. Twenty-one percent were used by patients without antibodies to prevent outdating. The remaining 6% had not yet been transfused by the end of the study period. From March 1, 2011, to August 31, 2011, we spent almost $200,000 on obtaining AG- blood. In the 6 months since we started antigen typing, we have saved approximately $110,000, the majority of which resulted from AG- blood provided to sickle patients. In addition, TAT for AG- units from our inventory significantly improved to 1 to 2 hours versus approximately 6 hours when obtained from our suppliers. CONCLUSION: Establishing an AG- inventory in a hospital-based blood bank is cost-effective and time-efficient.