Unusual spontaneous cold auto-hemagglutination phenomenon in blood units stored under blood bank condition: A retrospective analysis

BACKGROUND: Cold agglutinins (CA) are benign naturally occurring low titer autoantibodies present in most individuals. Those with moderate strength are found in infections, malignancies or autoimmune conditions with diagnostic importance. AIM: Present report deals with CA that brought spontaneous hemagglutination in blood units stored at 2-6°C. STUDY DESIGN: Over 32 months period between July 1993 and December 1995, blood units were inspected for spontaneous cold auto-hemagglutination (SpCA) phenomenon. The plasma from these units was separated and investigated for serological specificity using in house red cell panel and standard serological methods. RESULTS: Among 51,671 blood units, 112 units showed SpCA phenomenon. A rising trend seen in first half of study period significantly fell in remaining half. Specificities of the antibodies detected include anti-I (27), anti-i (53), anti-Pr (21) with remaining few being undetermined specificity. Absorption of serum using enzyme-treated red cells revealed a presence of anti-Pr among the cases, the two of which with new specificities that reacted preferentially with red cells from either new-born or adults and were tentatively named as anti-Pr(Fetal) and anti-Pr(adult), respectively. While 9 cases showed optimum reaction at neutral pH of 7, 68 (62%) cases reacted at pH 5.8 through 8.0, 28 (26%) cases preferred an acidic pH 5.8 and 4 cases opted an alkaline pH 8. Of 28 cases with antibodies preferentially reacting in acidic medium, 17 (60%) cases were anti-i and 7 (25%) cases were anti-Pr. CONCLUSION: Unique SpCA phenomenon observed in blood units stored under blood bank conditions seems to be due to CA developed in response to vector-borne infectious agents. Majority of the cases displayed their specificities, otherwise are rare to be encountered.