Question

Which of the following describes a positive Donath Landsteiner test indicating Paroxysmal Cold Hemoglobinuria (PCH) cause by an auto-anti-P most often found in young children after a viral or bacterial infection?

1) Tubes incubate at 4 C or at 37 C show hemolysis but the tubes incubated first in the cold and then at 37 C do not
2) Tubes incubated at 4 C show hemolysis but the tubes incubated at 37 degrees and first in the cold and then at 37 C do not
3) Tubes incubated at 4 C or 37 C do not show hemolysis but the tubes incubated first in the cold and then at 37 C do
4) Tubes incubated at 4 C do not show hemolysis but the tubes incubated at 37 degrees and first in the cold and then at 37 C do

Answer 1

A positive Donath Landsteiner test indicating PCH caused by an auto-anti-P most often found in young children after a viral or bacterial infection is described by option 2) Tubes incubated at 4°C show hemolysis, but the tubes incubated at 37°C and first in the cold and then at 37°C do not.

Step-by-step explanation:

A positive Donath Landsteiner test indicating paroxysmal cold hemoglobinuria (PCH) caused by an auto-anti-P most often found in young children after a viral or bacterial infection is described by option 2) Tubes incubated at 4°C show hemolysis, but the tubes incubated at 37°C and first in the cold and then at 37°C do not.

This test is based on the fact that in PCH, the auto-anti-P antibody attaches to red blood cells at low temperatures, causing them to lyse. When the tubes are incubated at 4°C, the auto-anti-P antibody attaches to the red blood cells and causes hemolysis. However, when the tubes are incubated first in the cold and then at 37°C, the antibody is not able to attach to the red blood cells at the higher temperature, preventing hemolysis.