Sickle cell anaemia: blood count and film may help exclude sickle cell disease in children.

Clinical bottom line (level 4)

  1. Children at risk of sickle cell disease who were anaemic, had a high reticulocyte count, abnormal red blood cell morphology, or sickle cells on microscopy were more likely to have sickle cell disease.
  2. Children with a normal haemoglobin level or reticulocyte count were unlikely to have sickle cell disease.
Losek et al: Annals of Emergency Medicine 1992; 21 (8): 915-918
Expires July 2004

The study

Setting: emergency department, children's hospital, USA

258 patients (aged 2 months to 21 years, 59% male) with fever; awaiting surgery; extremity or abdominal pain; stroke

Independent unblinded reference standard, applied in some patients from a ?consecutive appropriate spectrum.
Reference standard:
  • haemoglobin electrophoresis
Diagnostic test: haemoglobin, red cell morphology, reticulocyte count

The evidence


diagnostic test sickle cell disease sickle cell trait LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
age-adjusted anaemia 138 20 4.8
(3.2 to 7.2) 		0.87% 0.11
(0.063 to 0.19) 		0.022%
high reticulocyte count 141 16 6.2
(3.9 to 9.7) 		1.3% 0.085
(0.048 to 0.15) 		0.017%
abnormal red blood cell 134 5 19
(7.9 to 44) 		3.5% 0.12
(0.081 to 0.19) 		0.024%
sickle cells 85 0 -
(19 to -) 		100% 0.44
(0.37 to 0.53) 		0.088%
total 152 106

Comments

  1. 0.2% of black children have sickle cell disease. This has been used as a pre-test probability. Children with extremity pain would have a higher pre-test probability.
  2. The study was based on a retrospective chart review.
  3. The control group is not typical, with only children with sickle cell trait represented. This would underestimate the power of the tests.

Citation

  1. Losek JD, Hellmich TR, Hoffman GM: diagnostic value of anemia, red blood cell morphology, and reticulocyte count for sickle cell disease. Annals of Emergency Medicine 1992; 21 (8): 915-918
Contributor: Chris Ball and Clare Wotton, July 1999
Reviewer:

Clinical Question.
Patient possible sickle cell disease
Intervention or Exposure anemia, red blood cell morphology, reticulocyte count
Outcome sickle cell disease