Skip to main content


Log in

Likelihood ratios: A real improvement for clinical decision making?

  • Published:
European Journal of Epidemiology Aims and scope Submit manuscript


The concept of likelihood ratio has been advocated for several years as one of the better means to evaluate diagnostic tests and as a practical and valuable tool in clinical decision making. In this paper we review the basic concepts underlying the evaluation of diagnostic tests and we explore the properties and usefulness of both positive and negative likelihood ratios compared with sensitivity and specificity. Particular attention is given to the use of likelihood ratios in the clinical setting. Likelihood ratios have three main advantages: they are intuitive, they simplify the predictive value calculation and the overall evaluation of sequential testing. Disadvantages are the non-linearity and the necessity to recalculate probabilities in odds. Although they summarize the information contained in sensitivity and specificity, these characteristics are still necessary for certain clinical decisions. Since likelihood ratios have been promoted among physicians and medical students, we discuss examples of inappropriate use and misunderstandings in the medical literature: the frequent omission of confidence intervals, the choice of cut-off points based on likelihood ratios for positive test results only and the confusion between likelihood ratios for ranges and those for cut-off points.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or Ebook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others


  1. Albert A. On the use and computation of likelihood ratios in clinical chemistry. Clin Chem 1982; 28: 1113–1119.

    Google Scholar 

  2. Beck JR. Likelihood ratios: Another enhancement of sensitivity and specificity (editorial). Arch Pathol Lab Med 1986; 110: 685–686.

    Google Scholar 

  3. Fletcher RH, Fletcher SW, Wagner EH. Clinical epidemiology. Baltimore: Williams & Wilkins, 1988.

    Google Scholar 

  4. Giard RW, Hermans J. Interpretation of diagnostic cytology with likelihood ratios. Arch Pathol Lab Med 1990, 114: 852–854.

    Google Scholar 

  5. Goldenberg K, Verdain Barnes H, Redding MM. Diagnostic testing handbook for clinical decision making. Chicago: Yearbook Medical Publishers, 1989.

    Google Scholar 

  6. Guyatt GH, Patterson C, Ali M, et al. Diagnosis of iron-deficiency anemia in the elderly. Am J Med 1990; 88: 205–209.

    Google Scholar 

  7. Lacher DA. Special report: Predictive value derived from likelihood ratios: A superior technique to interpret quantitative laboratory results. Am J Clin Pathol 1987; 87: 673–676.

    Google Scholar 

  8. Linnet K. A review on the methodology for assessing diagnostic tests. Clin Chem 1988; 34: 1379–1386.

    Google Scholar 

  9. Pauker SG, Kopelman RI. Clinical Problem Solving. How sure is sure enough? N Engl J Med 1992; 326: 688–691.

    Google Scholar 

  10. Pellar TG, Leung YG, Henderson AR. A computer program for rapid generation of receiver operating characteristic curves and likelihood ratios in the evaluation of diagnostic tests. Ann Clin Biochem 1988; 25: 411–416.

    Google Scholar 

  11. Radack KL, Rouan G, Hedges J. The likelihood ratio An improved measure for reporting and evaluating diagnostic test results. Arch Pathol Lab Med 1986; 110: 689–693.

    Google Scholar 

  12. Sackett DL, Haynes RB, Tugwell P. Clinical epidemiology: A basic science for clinical medicine. Boston, Toronto: Little, Brown and Company, 1985.

    Google Scholar 

  13. Thornton RJ, Lilford RJ, Johnson N. Decision analysis in medicine. Br Med J 1992; 304: 1099–1103.

    Google Scholar 

  14. Feinstein AR. Clinical epidemiology: The architecture of clinical research. Philadelphia: Saunders, 1985.

    Google Scholar 

  15. Fletcher RH. Carcinoembryonic antigen. Ann of Int Med 1986; 104: 66–73.

    Google Scholar 

  16. Fagan TJ. Nomogram for Bayes's theorem (letter). N Engl J Med 1975; 293: 257.

    Google Scholar 

  17. Seymour DG, Green M, Vaz FG. Making better decisions: Construction of clinical scoring systems by the Spiegelhalter-Knill-Jones approach. Br Med J 1990; 300: 223–226.

    Google Scholar 

  18. Simel DL. Playing the odds. The Lancet 1985(i): 329–330.

  19. Goldstein BJ, Mushlin Al. Use of a single thyroxine test to evaluate ambulatory medical patients for suspected hypothyroidism. J Gen Intern Med, 1987; 2: 20–24.

    Google Scholar 

  20. Simel DL, Samsa GP, Matchar DB. Likelihood ratios with confidence: Sample size estimation for diagnostic test studies. J. Clin. Epidemiol 1991; 44 (8): 763–770.

    Google Scholar 

  21. Bulpitt CJ. Confidence intervals. Lancet 1987(i): 494–497.

  22. Leung FY, Galbraith LV, Jablonsky G, Henderson AR. Re-evaluation of the diagnostic utility of serum total creatine kinase and creatine kinase-2 in myocardial infarction. Clin Chem 1989; 35: 1435–1440.

    Google Scholar 

  23. Cochrane AL, Holland WW. Validation of screening procedures. Br Med Bull 1971; 27: 3–8.

    Google Scholar 

  24. Linnet K. Precision of sensitivity estmations in diagnostic test evaluations: Power functions for comparisons of sensitivities of two tests. Clin Chem 1985; 31: 574–580.

    Google Scholar 

  25. Sheps SB, Schechter MT. The assessment of diagnostic tests: A survey of current medical research. JAMA 1984; 252: 2418–2422.

    Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and permissions

About this article

Cite this article

Dujardin, B., Van den Ende, J., Van Gompel, A. et al. Likelihood ratios: A real improvement for clinical decision making?. Eur J Epidemiol 10, 29–36 (1994).

Download citation

  • Accepted:

  • Issue Date:

  • DOI:

Key words