CORE LABORATORY
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Alinity hq

COLD AGGLUTININ DISEASE

Description

All results of this patient sample were invalidated by Alinity hq. Left Shift and HGB Interf flags were present, and in the extended tab the “MCHC Out of Range. Check Sample Integrity.” message was displayed. This message may indicate a short sample or a clotted sample and leads to invalidation of the CBC; however, upon inspecting the sample, no clots were seen, and the sample volume was sufficient. The blood sample appeared macroscopically hemolytic and the smear review revealed clusters of RBCs, consistent with RBC autoagglutination. The presence of cold agglutinin was confirmed by the laboratory.

 

The invalidated results showed extremely low RBC and HGB values, associated with highly elevated MCH and MCHC. These findings have been associated with cold agglutinin disease in the literature (Zandecki, Part II, Topic). The HGB Interf flag was the consequence of the sample being hemolytic, causing discrepancy between the measured and the calculated HGB concentration.

 

Cold agglutinin disease is a type of autoimmune hemolytic anemia (AIHA) characterized by an immune reaction against RBC self-antigens (Swiecicki, McNicholl), leading to increased RBC clearance. The very low HGB concentration, the significantly elevated reticulocyte concentration and the presence of NRBC (confirmed by smear review) in this patient implies ongoing, significant hemolysis. Storing samples from patients with cold agglutinin disease at room temperature might cause serious preanalytical errors in the CBC analysis (Zandecki, Part II). Typical findings are low RBC count and high RBC indices due to RBC agglutination (Zandecki, Part II, Topic). These anomalies disappear when the sample is redrawn, kept at 37°C and analyzed promptly (Topic).

Numerical ResultsInvalid Data

 
WBC 34.5X 10e3/μL
NEU 22.3X 10e3/μL 64.7X % LEFT SHIFT
LYM 7.28X 10e3/μL 21.1X %
MONO 2.94X 10e3/μL 8.51X %
EOS .272X 10e3/μL .788X %
BASO .224X 10e3/μL 0.65X %
IG 1.47X 10e3/μL 4.25X %
NRBC 1.27X 10e3/μL
NR/W 3.67X

 
RBC 1.01X 10e6/μL
HGB 5.10X g/dL HGB Interf
HCT 8.06X %
MCV 80.2X fL
MCH 50.8X pg
MCHC 63.3X g/dL
RDW 31.1X %

 
RETIC 109.X 10e3/μL 10.9X %
IRF .484X
MCHr 55.2X pg

 
PLT 303.X 10e3/μL
MPV 7.42X fL
%rP 6.48X %

 
FIGURE 1. VOLUME (RBC):
RBC volume histogram
The RBC volume histogram shows a very wide base, with a tail extending over 170 fL, due to RBC agglutination. This is reflected by a very high RDW of 31.1%.
FIGURE 2. IAS X ALL (WBC):
Intermediate angles of light scatter plot
Even though results were invalidated due to the abnormally high MCHC caused by cold agglutinin, the WBC concentration is likely correct as clots or short sample were not present. The appearance of the WBC subpopulations show expected distribution. The presence of NRBC (red events) is evident in the lower left corner of the scatterplot.
Alinity hq Casebook. Cold agglutinin disease. ADD-00061876-v2 2019. p.22-23.

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Alinity h-series is available in select countries, not including the US.