Labs

The following results are from the complete blood count (CBC) the day you see the patient:

WBC (109/L)Hb (g/dL)MCV (fL)PLT (109/L)
11.26.3105403

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 109/L, RBC 4-6 x 1012/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45 fL, platelets (PLT) 150-450 x 109/L

Indeed, the reticulocyte count was elevated:

Reticulocyte count is:

  • 18.9% of total red cell count
  • 0.35 x 1012/L or 350 x 109/L

Focus on the absolute reticulocyte count. It keeps things simple. An absolute reticulocyte count >120 x 109/L is considered an appropriate response to anemia.

Therefore, this patient has a hyperproliferative anemia.

What is a typical baseline Hb for a patient with sickle cell anemia (HbSS)?

a
11-12 g/dL
b
10-11 g/dL
c
9-10 g/dL
d
8-9 g/dL
See next slide.
e
< 6 g/dL

Here are data on baseline hemoglobin concentration (Hb) from a large series of patients with HbSS:

Your patient presented with a hemoglobin concentration (Hb) of 6.3 g/dL. What do you predict her baseline Hb is?

a
< 6.3 g/dL
b
About 6.3 g/dL
c
> 6.3 g/dL
Correct. The Hb typically drops about 1 -2 g/dL during an acute pain crisis (see next slide).

Most patients with a veno-occlusive crisis (VOC) experience a drop in hemoglobin (Hb) of 1-2 g/dL. Here is a nice example from a single patient during the course of their pain crisis (note how the drop in Hb is accompanied by an increase in % reticulocytes [% retics]):

Let’s look at the baseline values for this patient’s complete blood count:

DateWBC (109/L)Hb (g/dL)MCV (fL)PLT (109/L)
Day of admission11.26.3105403
2 months earlier (baseline)7.37.9106313

What’s what: WBC, white blood cell count; Hb, hemoglobin; MCV, mean cell volume; MCHC, mean cellular hemoglobin concentration; RDW-SD, red cell distribution width-standard deviation; platelets, PLT; Normal values: WBC 5-10 x 109/L, RBC 4-6 x 1012/L, Hb 12-16 g/dL, Hct 35-47%, MCV 80-100 fL, MCHC 32-36 g/dL, RDW-SD < 45 fL, platelets (PLT) 150-450 x 109/L

Note the new leukocytosis and the drop in hemoglobin concentration (Hb).

The patient has a new leukocytosis. This is not unusual in a case of vaso-occlusive crisis. Here is her white cell differential:

These data indicate neutrophilia, lymphopenia and monocytosis (remember, focus on the absolute counts). How can we make these determinations? By referring to our cheat sheet!

Expressed as cell number x 106/L. Divide by 1000 to arrive at cell number x 109/L. It pays to be able to converse in both 106/L and 109/L because both are commonly referred to.

The patient’s white cell differential is consistent with stress.

Which of the following lab values would you expect to be elevated?

a
LDH
LDH is often increased at baseline in patients with sickle cell disease. During acute vaso-occlusive crises (VOC), even uncomplicated cases, the LDH may further increase secondary to added hemolysis and tissue infarction.
b
Bilirubin
The indirect (unconjugated) bilirubin may be increased at baseline in patients with sickle cell disease and further increased In an acute pain crisis, owing to an accentuation in hemolysis.
c
Haptoglobin
We would expect this to be low, not high. It may further decrease during an acute crisis, but it may also be elevated because it is an acute phase reactant.
d
Creatinine
e
Calcium

The results of her hemolysis labs are shown in the following table:

DateAST (IU/L)LDH (IU/L)Bilirubin (mg/dL)Haptoglobin (mg/dL)
Day of admission324082.9Undetectable
2 months earlier233840.586

Normal values: AST 040 IU/L, LDH 115-275 IU/L, bilirubin 0.0-1.5 mg/dL, Haptoglobin 30-200 mg/dL.

Other labs and imaging:

  • Creatinine and electrolytes were normal.
  • Chest X-ray in the emergency room was normal.

In summary, the labs reveal acute hemolysis on a background of low-grade hemolysis (based on the elevated LDH at baseline).

Are there any specific tests for vaso-occlusive (pain) crisis in sickle cell disease?

a
Yes
b
No
No, vaso-occlusive (pain) crisis is a diagnosis of exclusion.

Does this patient have vaso-occlusive crisis?

a
Yes
Yes, as defined by the sudden new onset of intense pain (though some present with gradual onset), that has no cause other than SCD lasting ≥ 4 hours requiring treatment with opioids or other analgesics.
b
No