Int J Med Sci 2009; 6(1):43-50. doi:10.7150/ijms.6.43 This issue
1. 061 Accident and Emergency Service. Huelva. Spain.
2. Department of Family Medicine, Primary Care Division of Seville and CIBER Fisiopatologia Obesidad y Nutrición (CB06/03). Instituto de Salud Carlos III. Spain.
3. Department of Statistics and Operations Research. University of Seville. Spain.
4. Research Support Unit. Virgen del Rocio University Hospital. Seville. Spain.
Objective: We obtained before an explanatory model with six dependant variables: age of the patient, total cholesterol (TC), HDL cholesterol (HDL-C), VLDL cholesterol (VLDL-C), alkaline phosphatase (AP) and the CA 19.9 tumour marker. Our objective in this study was to validate the model by means of the acquisition of new records for an additional analysis.
Design: Non-paired case control study.
Setting: Urban and rural hospitals and primary health facilities in Western Andalusia and Extremadura (Spain).
Patients: At both the primary care facilities and hospital level, controls were gathered in a prospective manner (n= 275). Cases were prospective and retrospective manner collected on (n=126).
Main outcome measures: Descriptive statistics, logistic regression and bootstrap analysis.
Results: The AGE (odds ratio 1.02; 95% CI 1.003-1.037) (p= 0.01), the TC (odds ratio 0.986; 95% C.I. 0.980-0.992) (p< 0.001) and the CA 19.9 (odds ratio 1.023; 95% C.I. 1.012- 1.034) (p<0.001) were the variables that showed significant values at logistic regression analysis and bootstrap. Berkson's bias was statistically assessed.
Conclusions: The model, validated by means of logistic regression and bootstrap analysis, contains the variables AGE, TC, and CA 19.9 (three of the original six) and has a level 4 over 5 according to the criteria of Justice et al. (multiple independent validations) [Ann. Intern. Med.1999; 130: 515].
Keywords: Multivariate explanatory model, non-paired case control study, sporadic carcinoma