THEORETICAL BASES FOR CRITICAL READING OF ARTICLES ABOUT DIAGNOSTIC TESTS IN NEUROLOGY

Abstract
As a consequence of the relevant role of diagnosis in decision making related to clinical practice, research and health management, the review of principles in which judgements about the quality of a diagnostic test are based is very convenient. After reviewing briefly the diagnostic reasoning types and approaches that show how clinical history, examination, experience, and theoretical knowledge may be combined, the main characteristics of a diagnostic test are reviewed. The statistical methods to quantify these properties are also shown. Reliability , understood as stability of results, may be determined by means of such statistics as kappa, interclass correlation coefficient, or percentage of agreement, according to the type of variable. Validity is the test attribute needed for the purpose for which it was designed. Some different aspects of this attribute, such as sensitivity, specificity, predictive values, likelihood ratios, etc. may be calculated and each of them is relevant to different aspects of the test validity. Finally a list of possible biases are analysed. It is proposed that if we follow the Evidence-Based Medicine guidelines for critical reading of articles on diagnostic tests, we will be able to assess the quality of a paper on this matter.

Key words
Diagnostic tests, characterization, indexes, critical reading, neurology

Bibliografía del artículo

1. Real Academia de la Lengua Española. En: Diccionario de la Lengua Española, 22 edic. http://buscon.rae.es/diccionario/drae.htm (acceso 14-12-2004).
2. Gifford DR, Mittman BS. Diagnostic reasoning in Neurology. Neurol Clinics 1996; 14:223- 238.
3. Díaz Guzmán J. Razonamiento diagnóstico en Neurología. Errores más comunes. Neurología 2003; 18 (Supl 2):3-10.
4. Gronseth GS. Diagnosing carpal tunnel syndrome. Syllabi CD-ROM (Marathon Multimedia). American Academy of Neurology 2003; 1PC.001-4.
5. Gómez de la Cámara A. Caracterización de pruebas diagnósticas. Neurología 2004; 19 (Supl 1):31-38.
6. Cohen J. A coefficient of agreement for nominal scales. Educ Psychol Meas 1960; 20:37-46.
7. Portney LG, Watkins MP. Foundations of Clinical Research. Applications and Practice. Norwalk, Conneticut: Appleton & Lange, 1993; 509-516.
8. Cohen J. Weighted kappa: Nominal scale agreement with provision for scaled disagreement or parcial credit. Psychol Bull 1968; 70:213-220.
9. Abraira V. Errores en las mediciones y clasificaciones clínicas: Precisión y validez. En: Material docente de la Unidad de Bioestadística Clínica del Hospital Ramón y Cajal. http://www.hrc.es/bioest/M_docente.html (acceso 17-12-2004).
10. Abraira V. El índice kappa. SEMERGEN 2000; 27:247-249.
11. Feinstein AR, Cicchetti DV. High agreement but low kappa: I. The problem of two paradoxes, J Clin Epidemiol 1990; 43:543-549.
12. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; i:307-310.
13. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977; 33:159-174.
14. Uebersax J. Intraclass correlation and related methods. En: Statistical methods for rater agreement. http://ourworld.compuserve.com/homepages/jsuebersax/agree.htm (acceso 17-12-2004).
15. Longstreth WT, Koepsell TD, Van Belle G. Clinical Neuropidemiology. I. Diagnosis. Arch Neurol 1987; 44:1091-1099.
16. Pozo F. Utilización clínica de las pruebas diagnósticas. En: Merino Sánchez J et al, Edits. Tratado de Epidemiología Clínica. Madrid: Dupont Pharma, 1995; 199-226.
17. Molinero LM. Valoración de pruebas diagnósticas. En: Páginas sobre bioestadística. http://www.seh-lelha.org/stat1.htm (acceso 18-12-2004).
18. Jaeschke R, Guyatt GH, Sackett DL, The Evidence Based Medicine Working Group. Users’ guides to the medical literature. III. How to use an article about a diagnostic test. B. What are the results and will they help me in caring for my patients JAMA 1994; 271:703-707.
19. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology. A basic science for clinical medicine, 2ª edn. Boston/Toronto: Little, Brown and Company, 1991.
20. Jaeschke R, Guyatt GH, Sackett DL, The Evidence Based Medicine Working Group. Users’ guides to the medical literature. III. How to use an article about a diagnostic test. A. Are the results of the study valid JAMA 1994; 271:389-391.
21. Sackett DL, Richardson WS, Rosenberg W, Haynes RB. Medicina basada en la evidencia (Edn. española). Madrid: Churchill Livingstone, 1997; 104-112.
22. Franklin GM. How to translate best evidence into best practice: Therapy, diagnosis, prognosis, and causation. Syllabi CD-ROM (Marathon Multimedia). American Academy of Neurology 2003; 1PC.001-1.