Luis Alberto López

Angiotensin-converting enzyme and alpha-2-macroglobulin gene polymorphisms are not associated with Alzheimer's disease in Colombian patients

Polymorphisms in alpha-2-macroglobulin (A2M) and angiotensin-converting enzyme (ACE) genes have been considered as risk factors for Alzheimers disease (AD) independently of the risk conferred by the apolipoprotein E sigma4 allele (APOEsigma4) in diverse populations. In the present study, we have analysed the distribution of genotypes and alleles of the insertion/deletion (I/D) polymorphisms of ACE and A2M in 83 AD patients and 69 normal controls in Colombia. Our results showed that there is no association between the I/D polymorphisms of ACE and A2M with AD (P = 0.788 and P = 0.538, respectively). Using logistic regression and multiple correlation analysis (MCA), we confirmed that the main risk factor associated and consistently grouped with AD patients in this population is APOE4, but this association was not observed with alleles and genotypes of ACE and A2M.

Basic aspects of the pathogenesis and prevention of non-melanoma skin cancer in solid organ transplant recipients: a review.

As numbers of transplant recipients and survival rates increase, the vulnerability of this population to several malignancies also rises. Non‐melanoma skin cancer (NMSC) carries the highest rates of morbidity and mortality in this population. To avoid these malignancies, it is necessary to identify particular risk factors in transplant recipients and to follow preventive protocols.

Association Analysis of Polymorphisms in TOMM40, CR1, PVRL2, SORL1, PICALM, and 14q32.13 Regions in Colombian Alzheimer Disease Patients.

Objective:We evaluated the association of several single-nucleotide polymorphisms in different genes including APOE, TOMM40, CR1, PVRL2, SORL1, PICALM, and GWA_14q32.13 in a Colombian sample of Late-Onset Alzheimer disease (LOAD) patients. Methods:A case-control study was conducted in 362 individuals (181 LOADs and 181 controls) to determine the association of single-nucleotide polymorphisms in APOE (e2, e3, and e4), TOMM40 (rs2075650), CR1 (rs665640), PVRL2 (rs6859), SORL1 (rs11218304), PICALM (rs3851179), and GWA_14q32.13 (rs11622883) with LOAD in a sample from Colombia. Results:We were able to confirm the previously reported association of the APOE4 allele with AD. In addition, we report a new significant association with rs2075650 of TOMM40 for LOAD in our sample. We did not detect any significant interaction between TOMM40 and APOE4 carriers (heterozygous or homozygous) for disease risk development. However, Kaplan-Meier survival analyses suggest that AD patients with TOMM40 allele rs2075650-G have an average age of disease onset of 6 years earlier compared with carriers of the A allele. In addition, the age of disease onset is earlier if APOE4/4 is present. Conclusion:Our findings suggest that rs2075650 of TOMM40 could be involved in earlier presentation of LOAD in the Colombian population.

Evaluating Statistical Methods Practiced in Two Important Areas of Quality Improvement

This paper presents evaluations and comparisons of statistical methods practiced in factor screening as well as in analysis with missing data. In quality performance evaluation studies using factorial experiments, the method of a normal probability plot is routinely used for screening out factors with insignificant effect on the quality characteristic. We demonstrate that the method of a normal probability plot for factor screening can be misleading. A screened out factor may turn out to be significant in the presence of certain interactions. Three methods of analysis in the presence of missing data for explanatory or response variables are considered under the multiple linear regression model by ignoring the missing data rows, substituting the corresponding column means from the data rows with no missing data, and substituting the Yates/EM algorithm estimates for the missing data. Five illustrative examples are given. In all examples, the third method has turned out to be the winner.