Thank you for playing along with this week’s “grammar lesson”! Most of you correctly identified the missing verb: Warmed.

When the sample arrived in the lab, it had a “sandy” or gritty appearance inside the EDTA tube. Under the microscope, the red cells weren’t just overlapping; they were physically stuck together in irregular, massive clumps, leaving large empty spaces on the slide.

This phenomenon is caused by Cold Agglutinins, typically IgM autoantibodies that react with the “I” or “i” antigens on the red cell surface at temperatures below 37^OC.

In the cold (room temperature), the pentameric IgM antibodies act like “bridges,” cross-linking multiple red cells into large aggregates. This is agglutination, which is morphologically distinct from rouleaux (where cells stack like coins due to high plasma proteins).

If the MCHS is “off the charts” and the RBC histogram looks like a mountain range, don’t trust the results. Warm the sample, re-run it, and make a new film. It’s the simplest fix for one of the most striking sights in haematology.