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.

Screening and Identification of Unexpected Red Cell Antibodies by Simultaneous LISS/Coombs and NaCl/Enzyme Gel Methods

We evaluated the clinical usefulness of simultaneous LISS/Coombs and NaCl/Enzyme testing using the gel method for screening and identification of unexpected antibodies in 15,014 samples. When unexpected antibodies were detected by either screening test, those antibodies were identified using both the LISS/Coombs and the NaCl/Enzyme gel test. The positive screening rates of the LISS/Coombs, NaCl/Enzyme, and combined tests (excluding 25 autoantibody cases) were 0.48%, 1.29%, and 1.39%, respectively. Among the 57 samples positive by both screening methods, the antibodies in 19.3% could be identified only by the NaCl/Enzyme method. Among the 137 samples positive only by NaCl/Enzyme screening, 74.5% showed positive results in antibody identification only by the NaCl/Enzyme test, although 7.3% were also positive in the LISS/Coombs test. The NaCl/Enzyme method thus showed about threefold higher detection rates than the LISS/Coombs method, especially in screening for Rh antibodies, and higher exact identification rates and discriminatory power for identifying mixed antibodies. Addition of the NaCl/Enzyme method to routine laboratory procedures may detect and identify considerable numbers of significant antibodies that might be missed if only the LISS/Coombs method is used.

Usefulness of NaCl/Enzyme Gel Test for the Identification of Unexpected Antibodies / 대한진단검사의학회지

BACKGROUND: The microcolumn assay technique offers significant advances in identification of unexpected antibodies; however, some erythrocyte antibodies still remain unidentified. To see if NaCl/Enzyme test is useful for the identification of antibodies, we compared the LISS/Coombs and NaCl/Enzyme tests for identification rates, and investigated an association between the frequency of each antibody and a history of transfusion or gestation. METHODS: From June 2004 to June 2005, antibody screening tests were carried out on 5,517 patients using the LISS/Coombs gel test (DiaMed AG, Switzerland). When antibodies were detected, antibody identification tests were carried out with the LISS/Coombs and NaCl/Enzyme gel tests (DiaMed AG) simultaneously. RESULTS: Unexpected antibodies were detected in 79 patients (1.43%). These antibodies were identified in 39 (49.4%), 59 (74.7%), and 68 patients (86.1%) by the LISS/Coombs test, the NaCl/Enzyme test, and the two tests combined, respectively. With the addition of the NaCl/ Enzyme test, unexpected antibodies were further identified in 29 cases (anti-Lewis, 14; anti-Rhesus, 13; and anti-P1, 2). On the other hand, 9 cases (anti-M, 5; anti-Fy(b), 3; and anti-N, 1) were identified by the LISS/Coombs test only. Of the unexpected antibodies found in patients without a previous history of transfusion or gestation, anti-Lewis (50.0%, 10/20) was the most common, while in patients with the history anti-Rhesus (48.1%, 26/54) was the most frequent. CONCLUSIONS: The NaCl/Enzyme combined with LISS/Coombs gel test was useful for the identification of unexpected antibodies, and antibodies found in patients without a previous history of transfusion or gestation were clinically less relevant than those found in patients with the history.