Improved detection of Mycobacterium tuberculosis in Peruvian children by use of a heminested IS6110 polymerase chain reaction assay.

A novel heminested IS6110 polymerase chain reaction (PCR) assay was evaluated as a tool for diagnosing tuberculosis in 222 children. In an analysis of 392 specimens (gastric aspirates, nasopharyngeal aspirates, and sputum samples), results of PCR were compared with those of 3 culture methods, acid-fast bacillus (AFB) staining, and clinical assessment by the Stegen-Toledo score. The sensitivity of PCR (67%) was comparable to that of the 3-culture method (71%) and was significantly higher than that of Löwenstein-Jensen culture (54%) or AFB stain (42%) for children with highly probable tuberculosis. PCR detection rates for culture-positive specimens were 100% for smear-positive samples and 76.7% for smear-negative samples. The specificity of PCR was 100% in control children. Compared with culture, PCR demonstrated a sensitivity of 90.4%, a positive predictive value of 89%, a specificity of 94%, and a negative predictive value of 95% (kappa=.85). With clinical assessment as the standard, PCR had a sensitivity of 71%, a positive predictive value of 92%, a specificity of 95%, and a negative predictive value of 79% (kappa=.67). PCR is a rapid and sensitive method for the early diagnosis of pediatric tuberculosis.

Wealth and its associations with enteric parasitic infections in a low-income community in Peru: use of principal component analysis.

The association of wealth and infections with Giardia, Cryptosporidium, Cyclospora, and microsporidia were examined in a longitudinal cohort conducted in Peru from 2001 to 2006. Data from 492 participants were daily clinical manifestations, weekly copro-parasitological diagnosis, and housing characteristics and assets owned (48 variables), and these data were used to construct a global wealth index using principal component analysis. Data were analyzed using continuous and categorical (wealth tertiles) models. Participant's mean age was 3.43 years (range = 0-12 years), with average follow-up of 993 days. Univariate and multivariate analyses identified significant associations between wealth and infections with Giardia and microsporidia. Participants with greater wealth indexes were associated with protection against Giardia (P < 0.001) and persistent Giardia infections (> 14 days). For microsporidia, greater wealth was protective (P = 0.066 continuous and P = 0.042 by tertiles). Contrarily, infections with Cryptosporidium and Cyclospora were independent of wealth. Thus, subtle differences in wealth may affect the frequency of specific parasitic infections within low-income communities.

Human caliciviruses as a cause of severe gastroenteritis in Peruvian children.

To define the role of human caliciviruses (HuCVs) in severe childhood gastroenteritis, fecal and paired serum samples from 233 Peruvian children hospitalized with gastroenteritis (case patients) and fecal samples from 248 control subjects were evaluated. Overall, 128 case patients (55%) demonstrated HuCV infection by either fecal (n=81 [35%]) or serological (n=96 [41%]) testing. HuCVs were more prevalent in fecal samples from case patients than those from control subjects (35% vs. 13%; P<.001). HuCV infection was more prevalent among case patients without another pathogen than in those who had a coinfecting pathogen (77% [40/52] vs. 49% [88/181]; P<.001). HuCVs appear to be an important cause of gastroenteritis in Peruvian children.