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OtherPractice

Complete blood count for screening?

G. Michael Allan and Jennifer Young
Canadian Family Physician October 2017; 63 (10) 772;
G. Michael Allan
Director of the PEER (Patients, Experience, Evidence, Research) Group and Professor in the Department of Family Medicine at the University of Alberta in Edmonton.
MD CCFP
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Jennifer Young
Family physician practising in Collingwood, Ont.
MD CCFP(EM)
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Clinical question

Is there evidence for screening with complete blood count (CBC) in asymptomatic, nonpregnant adults?

Bottom line

Neither CBC nor its components should be ordered for screening asymptomatic, nonpregnant adults, as it does not reduce mortality. Up to 11% of results are abnormal but less than 1% of results require management change. It is unclear which patients benefit and serious disease is almost never found.

Evidence

  • A systematic review of 16 RCTs on periodic health checks found that 4 RCTs included CBC components with other screening tests and reported no cancer-specific or overall mortality reduction.1

  • A population screening study found that in 1080 non-pregnant women aged 20 to 64, 11% were anemic but none had colon cancer.2

  • There were 11 observational case-finding studies:

    • -In 799 ambulatory patients, 11% of 475 leukocyte tests had abnormal results but no asymptomatic disease was identified.3

    • -Of 1540 CBC components tested, 6.4% had abnormal results, 1.2% were investigated, and 0.2% led to change.4

    • -Others studies had similar results.5

  • In 4 observational studies (214 to 1005 patients)6 on preoperative screening, management was changed in 0%, 0%, 0.2%, and 2% of cases, respectively.

  • In 2 observational studies (301 and 302 patients) on admission screening, about 11% had abnormal CBC components and 0.6% or less led to management changes.7,8

  • Management change does not mean patients benefited.

  • Harms of excessive investigation were not described.

Context

  • When diseases are uncommon (about 1% prevalence), only about 16% of abnormal results indicate real disease.9

    • -About 80% of abnormal leukocyte screening results were physiologic or test variance.2

    • -Most abnormal results (60%) resolved by 18 months.4

  • The Centers for Disease Control and Prevention, the US Preventive Services Task Force, and Choosing Wisely do not recommend screening with CBC.5 Only pregnancy screening is consistently advised.5

  • About 70% of primary care clinicians would order a screening CBC for a 55-year-old woman.10,11

Implementation

Complete blood count is not a useful test in asymptomatic individuals. The only “routine” bloodwork recommended is nonfasting lipid levels (in men ≥ 40 and women ≥ 50) every 5 years12 and hemoglobin A1c levels if the patient’s CANRISK score is above 14, with frequency depending on risk.13 Other bloodwork depends on symptoms, signs, or risks. Preprinted laboratory requisitions are discouraged,10 given the individualization of patient care.

Notes

Tools for Practice articles in Canadian Family Physician (CFP) are adapted from articles published on the Alberta College of Family Physicians (ACFP) website, summarizing medical evidence with a focus on topical issues and practice-modifying information. The ACFP summaries and the series in CFP are coordinated by Dr G. Michael Allan, and the summaries are co-authored by at least 1 practising family physician and are peer reviewed. Feedback is welcome and can be sent to toolsforpractice{at}cfpc.ca. Archived articles are available on the ACFP website: www.acfp.ca.

Footnotes

  • This article is eligible for Mainpro+ certified Self-Learning credits. To earn credits, go to www.cfp.ca and click on the Mainpro+ link.

  • Cet article se trouve aussi en français à la page 773.

  • Competing interests

    None declared

  • The opinions expressed in Tools for Practice articles are those of the authors and do not necessarily mirror the perspective and policy of the Alberta College of Family Physicians.

  • Copyright© the College of Family Physicians of Canada

References

  1. 1.↵
    1. Krogsbøll LT,
    2. Jørgensen KJ,
    3. Grønhøj Larsen C,
    4. Gøtzsche PC
    . General health checks in adults for reducing morbidity and mortality from disease. Cochrane Database Syst Rev 2012;(10):CD009009.
  2. 2.↵
    1. Elwood PC,
    2. Waters WE,
    3. Greene WJ,
    4. Wood MM
    . Evaluation of a screening survey for anaemia in adult non-pregnant women. Br Med J 1967;4(5581):714-7.
    OpenUrlFREE Full Text
  3. 3.↵
    1. Rich EC,
    2. Crowson TW,
    3. Connelly DP
    . Effectiveness of differential leukocyte count in case finding in the ambulatory care setting. JAMA 1983;249(5):633-6.
    OpenUrlCrossRefPubMed
  4. 4.↵
    1. Rüttimann S,
    2. Clémençon D,
    3. Dubach UC
    . Usefulness of complete blood counts as a case-finding tool in medical outpatients. Ann Intern Med 1992;116(1):44-50.
    OpenUrlCrossRefPubMed
  5. 5.↵
    1. Allan GM,
    2. Young J
    . CBC (confusing broad check) for screening? Edmonton, AB: Tools for Practice; 2017.
  6. 6.↵
    1. Czoski-Murray C,
    2. Lloyd Jones M,
    3. McCabe C,
    4. Claxton K,
    5. Oluboyede Y,
    6. Roberts J,
    7. et al
    . What is the value of routinely testing full blood count, electrolytes and urea, and pulmonary function tests before elective surgery in patients with no apparent clinical indication and in subgroups of patients with common comorbidities: a systematic review of the clinical and cost-effective literature. Health Technol Assess 2012;16(50):i-xvi, 1-159.
    OpenUrl
  7. 7.↵
    1. Frye EB,
    2. Hubbell FA,
    3. Akin BV,
    4. Rucker L
    . Usefulness of routine admission complete blood cell counts on a general medical service. J Gen Intern Med 1987;2(6):373-6.
    OpenUrlCrossRefPubMed
  8. 8.↵
    1. Mozes B,
    2. Haimi-Cohen Y,
    3. Halkin H
    . Yield of the admission complete blood count in medical inpatients. Postgrad Med J 1989;65(766):525-7.
    OpenUrlAbstract/FREE Full Text
  9. 9.↵
    1. Wians FH
    . Clinical laboratory tests: which, why, and what do the results mean? Lab Med 2009;40(2):105-13.
    OpenUrlCrossRef
  10. 10.↵
    1. Fung D,
    2. Schabort I,
    3. MacLean CA,
    4. Asrar FM,
    5. Khory A,
    6. Vandermeer B,
    7. et al
    . Test ordering for preventive health care among family medicine residents. Can Fam Physician 2015;61:256-62. (Eng), e165–73 (Fr).
    OpenUrlAbstract/FREE Full Text
  11. 11.↵
    1. Chacko KM,
    2. Feinberg LE
    . Laboratory screening at preventive health exams: trend of testing, 1978–2004. Am J Prev Med 2007;32(1):59-62.
    OpenUrlCrossRefPubMed
  12. 12.↵
    1. Allan GM,
    2. Lindblad AJ,
    3. Comeau A,
    4. Coppola J,
    5. Hudson B,
    6. Mannarino M,
    7. et al
    . Simplified lipid guidelines. Prevention and management of cardiovascular disease in primary care. Can Fam Physician 2015;61:857-67. (Eng), e439–50 (Fr).
    OpenUrlAbstract/FREE Full Text
  13. 13.↵
    1. Canadian Task Force on Preventive Health Care
    . Recommendations on screening for type 2 diabetes in adults. CMAJ 2012;184(15):1687-96. Erratum in: CMAJ 2012;184(16):1815.
    OpenUrlFREE Full Text
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Canadian Family Physician: 63 (10)
Canadian Family Physician
Vol. 63, Issue 10
1 Oct 2017
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Complete blood count for screening?
G. Michael Allan, Jennifer Young
Canadian Family Physician Oct 2017, 63 (10) 772;

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