Sickle cell anaemia: pulse oximetry may diagnose hypoxia.

Clinical bottom line (level 4)

  1. A third of well children with sickle cell anaemia had an oxygen saturation of <93%.
  2. Patients with an SaO 2 <93% usually did have hypoxia (LR+inf) .
  3. Pulse oximetry was unhelpful in excluding hypoxia.
Pianosi et al: Archives of Diseases in Childhood 1993; 68: 735-738
Expires May 2003

The study

Setting: university hospital, USA

20 patients (aged ?, ?% male) healthy sickle cell children

Excluded if
  • transfusion in the last three months



    • Independent unblinded reference standard, applied in all patients from a consecutive inappropriate spectrum.
    Reference standard:
    • capillary blood gas sample (taken using a lancet from a hand wrapped in a heated cloth for five minutes) (SpO2). Positive if <93%.
    Diagnostic test: pulse oximetry (SaO2). Positive if <93%.
    • Measurements were taken at rest and working at 50% maximum on an exercise bike.

    The evidence

    pre-test probability of SpO2 <93%: 37%, (95% CI: 15% to 59%)

    diagnostic test SpO2 <93% SpO2 =93% LR+
    (95% CI)    		 post-test probability LR-
    (95% CI)    		 post-test probability
    pulse oximetry 2 0 inf
    (1.3 to inf)     		100% 0.71
    (0.45 to 1.1)     		29%
    total 7 12

    Comments

    1. Data was only available for nineteen patients.
    2. Hand-capillary blood gas samples have not been validated against arterial samples, unlike earlobe sampling.
    3. The bottom line is that the fifth vital sign is not as helpful in sickle cell anaemia as it is in other disease states.

    Citation

    1. Pianosi P, Charge TD, Esseltine DW, et al: Pulse oximetry in sickle cell disease. Archives of Diseases in Childhood 1993; 68: 735-738
    Contributor: Chris Ball and Clare Wotton, May 2000
    Reviewer: Mona Nabulsi

    Clinical Question.
    Patient sickle cell anaemia
    Intervention or Exposure pulse oximetry
    Comparison capillary blood gas
    Outcome diagnosis of hypoxia