Unexpected red cell antibody detection by conditional combination of LISS/Coombs and NaCl/Enzyme gel tests at a tertiary care hospital in Korea: A 5-year study

BACKGROUND: A combination of the LISS/Coombs and enzyme methods is recommended for identifying unexpected antibodies. However, many laboratories in which tests are to be performed within the limits of medical fees covered by insurance, use only the LISS/Coombs method because the permissible medical fee is low as compared to the price of reagents required for both methods. The NaCl/Enzyme gel is used as a secondary assay when the LISS/Coombs gel test yields inconclusive results. We compared the frequency of unexpected antibody identified by LISS/Coombs gel with that obtained by the conditional combination of LISS/Coombs and NaCl/Enzyme gels. We aimed at establishing evidence-based guidelines for antibody testing. METHODS: From June 2007 to June 2012, antibody screening was performed for 69,986 samples; subsequently, antibodies were identified in samples showing positive screening results. These initial screenings and identifications were performed using the LISS/Coombs gel. We considered the results "inconclusive" when specific antibodies were not identified or reactions were too weak for accurate interpretation. For the inconclusive samples, we subsequently used NaCl/Enzyme gels. RESULTS: The overall detection rate of unexpected antibodies was 1.23%. Among the samples analyzed using NaCl/Enzyme gels, 40.2% showed results different from those obtained using LISS/Coombs gels. Moreover, 41.9% of samples with nonspecific reactions in LISS/Coombs gels showed clinically significant Rh or Kidd antibodies with NaCl/Enzyme gels. CONCLUSION: Considering both patient safety and cost effectiveness, we recommend the use of conditional combination of LISS/Coombs and NaCl/Enzyme gels for antibody detection, especially in laboratories that must perform tests within an established budget.