Application of Number Needed to Treat (NNT) - GOLD

84 Cazzola
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more recently, the newer measure of number needed to screen in
epidemiology.
An additional potential benefit of NNT lies in the learning
process that accompanies its adoption. The principles underlying
calculation of NNT are easily understood and link in logically with
the concepts of risk and effect of outcomes on such risk. Through
the simple background research that is needed, clinicians wishing
to apply clinical evidence to their practice can benefit from a
greater understanding of how the parameters used to generate
NNTs, relative and absolute risk, are calculated.
As demonstrated in the present review, NNT is becoming more
widely adopted in respiratory medicine. Its recent endorsement by
the Consolidated Standards of Reporting Trials (CONSORT)
guidelines [36] means that NNT is likely to be used more frequently
in the medical literature. Physicians are therefore encouraged to
consider NNT data alongside other established measures when
selecting therapeutic interventions for respiratory medicine.
15. Halliday HL. Postnatal steroids and chronic lung disease in the newborn. Paediatr
Respir Rev 2004; 5 Suppl. A: S245-8
16. Stanton WR, Lowe JB, Moffatt J, et al. Randomised control trial of a smoking
cessation intervention directed at men whose partners are pregnant. Prev Med
2004; 38: 6-9
17. Shah SS, Ohlsson A, Halliday H, et al. Inhaled versus systemic corticosteroids for
preventing chronic lung disease in ventilated very low birth weight preterm
neonates. Cochrane Database Syst Rev 2003; (1): CD002058
18. Ho JJ, Subramaniam P, Henderson-Smart DJ, et al. Continuous distending pressure
for respiratory distress syndrome in preterm infants. Cochrane Database Syst
Rev 2002; (2): CD002271
19. Davis PG, Henderson-Smart DJ. Extubation from low-rate intermittent positive
airways pressure versus extubation after a trial of endotracheal continuous
positive airways pressure in intubated preterm infants. Cochrane Database Syst
Rev 2001; (4): CD001078
20. Abramson MJ, Puy RM, Weiner JM. Allergen immunotherapy for asthma. Cochrane
Database Syst Rev 2003; (4): CD001186
21. Powell H, Gibson PG. Inhaled corticosteroid doses in asthma: an evidence-based
approach. Med J Aust 2003; 178: 223-5
22. Rowe BH, Spooner CH, Ducharme FM, et al. Corticosteroids for preventing
relapse following acute exacerbations of asthma. Cochrane Database Syst Rev
2001; (1): CD000195
23. Charlton BG. Numbers needed to treat derived from meta-analysis: are an absurdity.
BMJ 1999; 319: 1199
Acknowledgments
24. Smeeth L, Haines A, Ebrahim S. Numbers needed to treat derived from metaanalyses:
sometimes informative, usually misleading. BMJ 1999; 318: 1548-51
25. D’Amico R, Deeks JJ, Altman DG. Numbers needed to treat derived from meta-
The author would like to thank AstraZeneca Italy for financial support.
analysis: length of follow up is poorly reported. BMJ 1999; 319: 1200
The author would also like to thank Adis International Ltd for assistance in the
26. Hopayian K, McGough J. Numbers needed to treat derived from meta-analysis:
preparation of this manuscript. The author has received fees for speaking and using patient years may also be misleading. BMJ 1999; 319: 1199-200
consulting and/or financial support for attending meetings from AstraZeneca
27. Moore A, McQuay H. Numbers needed to treat derived from meta analysis: NNT is
and GlaxoSmithKline. a tool, to be used appropriately. BMJ 1999; 319: 1200
28. Jain BP. Number needed to treat and relative risk reduction. Ann Intern Med 1998;
128: 72-3
References
29. Lui KJ. A simple logical solution to eliminate the limitations of using the number
1. Fahey T, Griffiths S, Peters TJ. Evidence based purchasing: understanding results
needed to treat. Eval Health Prof 2004; 27: 206-14
of clinical trials and systematic reviews. BMJ 1995; 311: 1056-9
30. Halvorsen PA, Kristiansen IS. Decisions on drug therapies by numbers needed to
2. Forrow L, Taylor WC, Arnold RM. Absolutely relative: how research results are treat: a randomized trial. Arch Intern Med 2005; 165: 1140-6
summarized can affect treatment decisions. Am J Med 1992; 92: 121-4
31. Szafranski W, Cukier A, Ramirez A, et al. Efficacy and safety of budesonide/
3. Malenka DJ, Baron JA, Johansen S, et al. The framing effect of relative and formoterol in the management of chronic obstructive pulmonary disease. Eur
absolute risk. J Gen Intern Med 1993; 8: 543-8 Respir J 2003; 21: 74-81
4. Naylor CD, Chen E, Strauss B. Measured enthusiasm: does the method of reporting
32. Calverley PM, Boonsawat W, Cseke Z, et al. Maintenance therapy with budesonide
trial results alter perceptions of therapeutic effectiveness? Ann Intern Med
and formoterol in chronic obstructive pulmonary disease. Eur Respir J 2003;
1992; 117: 916-21
22: 912-9
5. Evidence-Based Medicine Working Group. Evidence-based medicine: a new ap-
33. Halpin D, Stahl E, Lundback B, et al. Treatment costs and number needed to treat
proach to teaching the practice of medicine. JAMA 1992; 268: 2420-5
(NNT) with budesonide/formoterol to avoid one exacerbation of COPD [ab-
6. Cook RJ, Sackett DL. The number needed to treat: a clinically useful measure of
stract plus poster]. In: 100 th International Conference of the American Thoracic
treatment effect. BMJ 1995; 310: 452-4
Society; 2004 May 21-26; Florida. Am J Respir Crit Care Med 2004 May; 169
7. McQuay HJ, Moore RA. Using numerical results from systematic reviews in Suppl.: A770
clinical practice. Ann Intern Med 1997; 126: 712-20
34. Halpin DM. Evaluating the effectiveness of combination therapy to prevent COPD
8. Barratt A, Wyer PC, Hatala R, et al. Tips for learners of evidence-based medicine:
exacerbations: the value of NNT analysis. Int J Clin Pract 2005; 59: 1187-94
1. Relative risk reduction, absolute risk reduction and number needed to treat.
CMAJ 2004; 171: 353-8
35. Calverley P, Pauwels R, Vestbo J, et al. Combined salmeterol and fluticasone in the
9. Laupacis A, Sackett DL, Roberts RS. An assessment of clinically useful measures
treatment of chronic obstructive pulmonary disease: a randomised controlled
of the consequences of treatment. N Engl J Med 1988; 318: 1728-33
trial. Lancet 2003; 361: 449-56
10. Altman DG, Andersen PK. Calculating the number needed to treat for trials where 36. Altman DG, Schulz KF, Moher D, et al. The revised CONSORT statement for
the outcome is time to an event. BMJ 1999; 319: 1492-5
reporting randomized trials: explanation and elaboration. Ann Intern Med 2001;
11. Rembold CM. Number needed to screen: development of a statistic for disease
134: 663-94
screening. BMJ 1998; 317: 307-12
12. Smucny J, Fahey T, Becker L, et al. Antibiotics for acute bronchitis. Cochrane
Database Syst Rev 2004; (4): CD000245
Correspondence and offprints: Prof. Mario Cazzola, Dipartimento di
13. Altman DG. Confidence intervals for the number needed to treat. BMJ 1998; 317:
Pneumologia, Unità di Pneumologia ed Allergologia e Settore di Farmaco-
1309-12
logia Clinica Respiratoria, Ospedale ad Alta Specializzazione A. Cardarelli,
14. Reveiz L, Cardona AF, Ospina EG. Antibiotics for acute laryngitis in adults. Via del Parco Margherita 24, 80121 Napoli, Italy.
Cochrane Database Syst Rev 2005 Jan; (1): CD004783
E-mail: mcazzola@qubisoft.it
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