June 2013. Volume 9. Number 2

Unblinded assessment of subjective measurement scales overestimates the effect

 
 
 
 
 
 
 
 
 
 
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AVC | Critically appraised articles

Hróbjartsson A, Thomsen AS, Emanuelsson F, Tendal B, Hilden J, Boutron I, et al. Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors. CMAJ. 2013 Mar 5;185:E201-11. Epub 2013 Jan 28.
Reviewers: Ochoa Sangrador C1, Andrés de Llano JM2.
1Servicio de Pediatría. Hospital Virgen de la Concha. Zamora. España.
2Servicio de Pediatría. Hospital General del Río Carrión. Palencia. España.
Correspondence: Carlos Ochoa Sangrador. Email: cochoas@meditex.es
Reception date: 01/05/2013
Acceptance date: 08/05/2013
Publication date: 16/05/2013

Abstract

Authors' conclusions: there is an observer bias in randomized clinical trials with results of subjective measurement scale. Lack of blinding in evaluating the results in these trials increases a quarter of the standard deviation of the measuring scale used.

Reviewers' commentary: unblinded assessment of subjective effect measures seems to cause an overestimation of the effect in epidemiological studies. However, the magnitude of the estimated error in the studies of this review can not be generalized. Any study that uses subjective scale measures should consider employing masking techniques or at least try to control or quantify the potential mistake.

How to cite this article

Ochoa Sangrador C, Andrés de Llano JM. La valoración no enmascarada de escalas de medida subjetivas sobrestima el efecto. Evid Pediatr. 2013;9:27.

AVC | Critically appraised articles

Hróbjartsson A, Thomsen AS, Emanuelsson F, Tendal B, Hilden J, Boutron I, et al. Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors. CMAJ. 2013 Mar 5;185:E201-11. Epub 2013 Jan 28.
Reviewers: Ochoa Sangrador C1, Andrés de Llano JM2.
1Servicio de Pediatría. Hospital Virgen de la Concha. Zamora. España.
2Servicio de Pediatría. Hospital General del Río Carrión. Palencia. España.
Correspondence: Carlos Ochoa Sangrador. Email: cochoas@meditex.es
Reception date: 01/05/2013
Acceptance date: 08/05/2013
Publication date: 16/05/2013

How to cite this article

Ochoa Sangrador C, Andrés de Llano JM. La valoración no enmascarada de escalas de medida subjetivas sobrestima el efecto. Evid Pediatr. 2013;9:27.

References

  1. Hróbjartsson A, Thomsen AS, Emanuelsson F, Tendal B, Hilden J, Boutron I, et al. Observer bias in randomised clinical trials with binary outcomes: systematic review of trials with both blinded and non-blinded  outcome assessors. BMJ. 2012;344:e1119.
  2. Hojat M, Xu G. A visitor's guide to effect sizes: statistical significance versus practical (clinical) importance of research findings. Adv Health Sci Educ Theory Pract. 2004;9:241-9.
16/05/2013

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