Ask the Experts
Inconsistent Relationship Between
Hemoglobin and Hematocrit
An inconsistent relationship between hemoglobin (HGB)
and hematocrit (HCT) is a common clue to the presence
of analytic artifact in an individual patient's CBC count
results. Technologists should always be alert for violations of the "rules of three and nine":
Relationship
RBC x 9 = HCT
RBC x 3 = HGB
HGB x 3 = HCT
Patient's Values
Expected
Observed
33.5
29.4
9.6
7.7
23.1
29.4
The laboratory seems to have considered several common reasons for hemoglobin/hematocrit inconsistency, only
some of which could be possible in the situation described
in Ms Kling's letter. Lipemia or jaundice spuriously elevates the hemoglobin level and produces an HCT/HGB
ratio of less than 3:1 rather than the high ratio of 3.8:1
observed by Kling. Cryoglobulins and leukocyte fragments could have falsely elevated the red cell count, but
these causes were excluded. One primary measurement
was rechecked by an alternate method. The spun hematocrit was 24%, suggesting that the original hemoglobin
value was also correct (24/3 = 8). If this is so, the original
red count or MCV must have been falsely increased (Coulter HCT = MCV x RBC). Most of the common causes for
elevated MCV were excluded, as Kling indicated. Autoagglutinins would be seen on the smear, and in any case,
the HCT/HGB ratio would be low, not high. Hyperglycemic osmotic matrix effects that produce swelling of the
red cells in diluent is a possibility, but the "correct" MCV
8 6 8 LABORATORY MEDICINE • VOL. 18, NO. 12, DECEMBER 1987
in this situation, from the data described, would be expected to be about 65 fL. Van Voolen and co-workers indicated a 5-fL MCV increase occurs for every 1,000-mg/
dL increase in glucose at 37 °C, suggesting that the patient's glucose level would have been about 3,000 mg/dL.
I suspect the laboratory would have noted this if it had
occurred. Occasionally, the red count can be elevated by
small particulates such as microdots or air bubbles in the
aspiration lines. If such particles are small enough, they
will be gated in as red cell sized by the analyzer. Debris
seems to be a special problem in CBCs from dialysis units.
The following is a CBC count from a dialysis patient with
a pattern similar to that reported by Kling:
WBC
RBC
HGB
HCT
MCV
MCH
MCHC
RDW
3.6 x 109/L
4.11 x 1012/L
6.1 g/dL—
28.2 %—HCT/HGB ratio 3.6:1
68.6 fL
14.8 pg
21.5 g/dL
20.5 units
Verification showed that the hemoglobin level was correct, and the spun HCT was 19.9%. There were no grossly
observable clots in the EDTA tube. Tiny bubbles can be
introduced into the sample lines by briefly withdrawing
the sample aspirator tip from the blood during aspiration
and then reinserting it. Experimental counts 1 and 2 are
replicates; count 3 was produced from the same tube by
withdrawing and reinserting the blood.
WBC
RBC
HGB
HCT
MCV
MCH
MCHC
1
6.8
4.83
14.1
42.7
88.4
29.3
33.1
2
6.9
4.85
14.0
42.7
88
28.9
32.9
3
0.6
1.63
1.5
14.2
87.3
9.0
10.4
The WBC count and hemoglobin level fell to a tenth of
their original values; the red count decreased only by twothirds. The instrument, a Coulter S + II, was apparently
counting small bubbles as red cells, producing the absurd
values for MCH and MCHC. I suspect that the results
reported by Kling were due to bubbles or microdots, but
this cannot be proven after the fact. In such a situation,
results violating the expected relationships between interdependent parameters should not be released before
rechecking at least one and preferably two of the primary
measurements—RBC, HCT, and HGB—by an alternate
method. Releasing data after rechecking on the original
analyzer is not sufficient, as Ms Kling found out.
Richard A. Savage, MD
Ashtabula County Medical Center
Ashtabula, Ohio
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Our institution is currently using the Coulter S550 for
CBC counts. Recently a technologist sent out the following
values:
15.4 WBC
3 Bands
+ 3 Hypochromic
3.72 RBC
87 Polys
+2 Anisocytosis
7.7 HGB
10 Lymphs
+2 Poikilocytosis
29.4 HCT
+2 Polychromatophilia
79 MCV
+1 Macrocytes
+ Target Cells
Platelet Count 295,000
The technologist repeated her work and accepted the results as correct in view of the very high red count. The
physician was very critical of her work because the H&H
did not match. The technologist then did a 'spun hematocrit' with 24% as the reported result.
Interference by lipemia, an elevated white count, and cryoglobulins were ruled out.
Which hematocrit is correct?
Gail Kling, MT(ASCP)BB
Peekskill Community Hospital
Peekskill, NY