No abstract

A nationwide community-based survey for Helicobacter pylori infection had not been done. This study sought to determine the seroprevalence of infection in Mexico, and the socioeconomic and demographic variables that are risk factors for infection. The survey assessed 11,605 sera from a sample population representing persons ages 1-90 years from all socioeconomic and demographic levels and from all regions of Mexico. Antibodies against H. pylori were studied by ELISA using whole cell antigen. Among the findings were that 66% of the population was infected and that age was the strongest risk factor for infection. By age 1 year, 20% were infected and by age 10 years, 50% were infected. Crowding (odds ratio [OR], 1.4), low educational level (OR, 2.42), and low socioeconomic level (OR, 1.43) were risk factors for infection. Prevalence was similar in urban and in rural communities (OR, 0.95). This study is the largest community-based seroepidemiologic study of H. pylori to date.

The susceptibilities to three antimicrobials of 195 Helicobacter pylori strains isolated from Mexican patients is reported; 80% of the strains were resistant to metronidazole, 24% were resistant to clarithromycin, and 18% presented a transient resistance to amoxicillin. Resistance to two or more antimicrobials increased significantly from 1995 to 1997.

Objective-To evaluate whether sensitivity and specificity of tachypnoea for the diagnosis of pneumonia change with age, nutritional status, or duration of disease. Methods-Diagnostic testing of 110 children with acute respiratory infection, 51 of whom presented with tachypnoea. The gold standard was a chest roentgenogram. Thirty five children had a radiological image of pneumonia; 75 were diagnosed as not having pneumonia. Sensitivity, specificity, and percentage of correct classification of tachypnoea, by itself or in combination with other clinical signs for all children, by age groups, nutritional status, and disease duration were calculated. Results-Tachypnoea as the sole clinical sign showed the highest sensitivity (74%) and a specificity of 67%; 69% of cases were classified correctly. Sensitivity was reduced when other clinical signs were combined with tachypnoea, and there was no significant increase in correct classification, although specificity increased to 84%. In children with a disease duration of less than three days, tachypnoea had a lower sensitivity and specificity (55% and 64%, respectively), and a lower percentage of correct classification (62%). In children with low weight for age (< 1 Z-score), tachypnoea had a sensitivity of 83%, a specificity of 48%, and 60% correct classification. Sensitivity and specificity did not vary with age groups. Conclusions-Tachypnoea used as the only clinical sign is useful for identifying pneumonia in children, with no significant variations for age. In children with low weight for age, tachypnoea had higher sensitivity, but lower specificity. However, during the first three days of disease, the sensitivity, specificity, and percentage of correct classification were significantly lower. (Arch Dis Child 2000;82:41-45)