Standardization of a colorimetric technique for determination of enzymatic activity of diamine oxidase (DAO) and its application in patients with clinical diagnosis of histamine intolerance.

BACKGROUND: Diamine Oxidase (DAO) has an essential role for degradation of exogenous histamine in the intestine; thus, histamine intolerance (HI) mainly has been correlated to a low concentration and/or activity of this enzyme. The objective of the study was to standardize a colorimetric technique to measure the enzymatic activity (function) of hDAO to then apply it to a series of 22 patients with a clinical diagnosis of HI. METHODS: For the standardization variables such as volume and type of sample, incubation time, wavelength of maximum absorption, types of substrates, and concentration of oxidized ascorbate were evaluated. Then the activity and concentration of DAO was determined in 22 patients diagnosed with HI and 22 healthy subjects. RESULTS: The mean of serum DAO concentration in the 22 patients was of 9.268 ± 1.124 U/mL. The mean of serum DAO concentration in the 22 controls was of 20.710 ± 2.509 U/mL, being significantly higher (P value 0.0002) the mean of the samples. The mean of serum DAO activity of the patients was of 1.143 ± 0.085 U/L and the controls was 1.533 ± 0.119 U/L, significantly greater than the patients (P value 0.011). In addition, the sensitivity of both techniques was 0.63. In the measuring of DAO concentration the specificity was 0.9, constituting a good diagnostic test, especially to rule out the true negatives. The determination of DAO activity had a specificity of 0.68. CONCLUSIONS: Although we used a small number of patients and controls and the absorbance values were lower than expected, statistically significant differences were found in the levels of concentration and DAO activity between the patients with histamine intolerance and the controls. Therefore, the measuring of DAO concentration and DAO activity is a good diagnostic strategy for study suspect cases of HI. The simultaneous use of both assays allows to reduce positive and negative false results, for example, patients with normal DAO levels that could present a dysfunction in the activity of this enzyme.

Malnutrition and the presence of intestinal parasites in children from the poorest municipalities of Mexico.

BACKGROUND: For many years Chiapas, Mexico's poorest state, has had the highest rate of child mortality due to intestinal infections of unknown etiology in the country. To begin identifying the infectious agents, our work determined the prevalence of intestinal parasites as well as malnutrition in children from Chiapas's three most impoverished municipalities: Pantepec, Chanal, and Larrainzar. METHODOLOGY: In this cross-sectional study, conducted between January and November 2009, we assessed the prevalence of intestinal parasites by means of coproparasitological analysis in children <5 years of age (N=250) from three of the marginalized municipalities: Pantepec, Chanal and Larrainzar. The prevalence of malnutrition was then assessed using the Mexican official norm NOM-031-SSA2-1999 and WHO criteria. We evaluated the association between age (breast-fed and pre-school children) with parasites and nutritional status. RESULTS: Our analysis revealed the highest prevalence of intestinal parasites in children from Pantepec (62.8%), followed by Chanal (47.3%), and then Larrainzar (11.9 %). The nematode Ascaris lumbricoides was the most prevalent enteroparasite (33.6%). Anthropometric analysis revealed that >40% of children represented varying degrees of malnutrition and a marked constitutional delay in growth. A very high prevalence of stunting was also recorded in children from Chanal and Larrainzar (70% and 55%, respectively). An association between infection with intestinal parasites and malnutrition was observed in Pantepec. Preschool-age children were more likely to be infected with intestinal parasites. CONCLUSION: Our results indicate the urgent need for interventions in order to 1) improve the nutritional status of children and 2) reduce infection rates of enteric parasites.

HIV-1 tropism: a comparison between RNA and proviral DNA in routine clinical samples from Chilean patients.

BACKGROUND: HIV in Chile has a notification rate of 0.01%. Coreceptor antagonists are a family of antiretroviral drugs that are used with the prior knowledge of patients HIV-1 tropism. Viral RNA-based tropism detection requires a plasma viral load ≥1000 copies/mL, while proviral DNA-based detection can be performed regardless of plasma viral load. This test is useful in patients with low or undetectable viral loads and would benefit with a proper therapy. The aim of this study was to determine the correlation between HIV RNA and proviral genotypic DNA tropism tests. FINDINGS: Forty three Chilean patients were examined using population-based V3 sequencing, and a geno2pheno false-positive rate (FPR) cutoff values of 5, 5.75, 10 and 20%. With cutoff 5.75% a concordance of 88.4% in tropism prediction was found after a simultaneous comparison between HIV tropism assessment by RNA and DNA. In total, five discrepancies (11.6%) were found, 3 patients were RNA-R5/DNA-X4 and two were RNA-X4/DNA-R5. Proviral DNA enabled the prediction of tropism in patients with a low or undetectable viral load. For cutoff 5 and 5.75% genotypic testing using proviral DNA showed a similar sensitivity for X4 as RNA. We found that the highest sensitivity for detecting the X4 strain occurred with proviral DNA and cutoff of 10 and 20%. Viral loads were higher among X4 strain carriers than among R5 strain carriers (p < 0.05). CONCLUSIONS: A high degree of concordance was found between tropism testing with RNA and testing with proviral DNA. Our results suggest that proviral DNA-based genotypic tropism testing is a useful option for patients with low or undetectable viral load who require a different therapy.