Zhouwen Liu

Viral etiologies of infant bronchiolitis, croup and upper respiratory illness during 4 consecutive years.

Background: Prospective data on viral etiology and clinical characteristics of bronchiolitis and upper respiratory illness (URI) in infants are limited. Methods: This prospective cohort enrolled previously healthy term infants during inpatient or outpatient visits for acute URI or bronchiolitis during September to May 2004 to 2008. Illness severity was determined using an ordinal bronchiolitis severity score. Common respiratory viruses were identified by real-time reverse-transcriptase polymerase chain reaction. Results: Of 648 infants, 67% were enrolled during inpatient visits and 33% during outpatient visits. Seventy percent had bronchiolitis, 3% croup and 27% URI. Among infants with bronchiolitis, 76% had respiratory syncytial virus (RSV), 18% human rhinovirus (HRV), 10% influenza, 2% coronavirus, 3% human metapneumovirus and 1% parainfluenza virus. Among infants with croup, 39% had HRV, 28% parainfluenza virus, 28% RSV, 11% influenza, 6% coronavirus and none human metapneumovirus. Among infants with URI, 46% had HRV, 14% RSV, 12% influenza, 7% coronavirus, 6% parainfluenza virus and 4% human metapneumovirus. Individual viruses exhibited distinct seasonal, demographic and clinical expression. Conclusions: The most common infections among infants seeking care in unscheduled medical visits for URI or bronchiolitis were RSV and HRV. Demographic differences were observed between patients with different viruses, suggesting that host and viral factors play a role in phenotypic expression of viral illness.

Relationship of maternal vitamin D level with maternal and infant respiratory disease

OBJECTIVE The objective of the study was to investigate the association of maternal vitamin D and maternal asthma and infant respiratory infection severity. STUDY DESIGN The study included cross-sectional analyses of 340 mother-infant dyads enrolled from September to May 2004-2008 during an infant viral respiratory infection. Maternal vitamin D levels were determined from enrollment blood specimens. At enrollment, we determined self-reported maternal asthma and infant respiratory infection severity using a bronchiolitis score. We assessed the association of maternal vitamin D levels and maternal asthma and infant bronchiolitis score in race-stratified multivariable regression models. RESULTS The cohort was 70% white, 19% African American, and 21% had asthma. Overall, the median maternal vitamin D level was 20 ng/mL (interquartile range, 14-28). Among white women, a 14 ng/mL increase in vitamin D was associated with a decreased odds of asthma (adjusted odds ratio, 0.54; 95% confidence interval, 0.33-0.86). Maternal vitamin D was not associated with infant bronchiolitis score. CONCLUSION Higher maternal vitamin D levels were associated with decreased odds of asthma.

Agreement of Blood Spot Card Measurements of Vitamin D Levels with Serum, Whole Blood Specimen Types and a Dietary Recall Instrument

Background The ability to measure 25-hydroxyvitamin D (25OHD) levels from blood spot cards can simplify sample collection versus samples obtained by venipuncture, particularly in populations in whom it is difficult to draw blood. We sought to validate the use of blood spot samples for the measurement of 25OHD compared to serum or whole blood samples and correlate the measured levels with intake estimated from dietary recall. Methods Utilizing 109 biological mothers of infants enrolled in the Tennessee Childrens Respiratory Initiative cohort, we measured 25OHD levels through highly selective liquid chromatography–tandem mass spectrometry on samples from blood spot cards, serum, and whole blood collected at enrollment. Dietary questionnaires (n = 65) were used to assess 25OHD intake by dietary recall. Sample collection measures were assessed for agreement and 25OHD levels for association with dietary 25OHD intake. Results The mean absolute differences (95%CI) in 25OHD levels measured between whole blood and blood spot (n = 50 pairs) or serum and blood spot (n = 20) were 3.2 (95%CI:1.6, 4.8) ng/ml and 1.5 (95%CI:−0.5,3.4) ng/mL. Intake by dietary recall was marginally associated with 25OHD levels after adjustment for current smoking and race in linear regression. Discussion 25OHD levels determined by mass spectrometry from blood spot cards, serum and whole blood show relatively good agreement, although 25OHD levels are slightly lower when measured by blood spot cards. Blood spot samples are a less invasive means of obtaining 25OHD measurements, particularly in large population-based samples, or among children when venipuncture may decrease study participation.

Increased healthcare resource utilization for acute respiratory illness among Latino infants.

OBJECTIVE To examine healthcare resource utilization for acute respiratory illness in Latino infants compared with other racial/ethnic groups. STUDY DESIGN We studied 674 term-born, previously healthy infants brought in for an unscheduled healthcare visit for an acute respiratory illness. The predictor variable was infant race/ethnicity, and the primary outcome was healthcare resource utilization, adjusted for age and disease severity. RESULTS The cohort was 14% Latino, 52% white, 22% African American, and 12% other race/ethnicity. More than one-third (37%) of the mothers of Latino infants were Spanish-speaking. The bronchiolitis severity score was higher (indicating more severe disease) in white infants (median, 6.0; IQR, 3.0-9.0 on a scale of 0-12) compared with Latino (median, 3.0; IQR, 1.0-6.0) and African American (median, 3.5; IQR, 1.0-6.0) infants (P < .001 for the comparison of all groups). Disease severity was similar in Latino and African American infants (P = .96). Latino infants were the most likely to receive antibiotics (58%, compared with 47% of whites and 34% of African Americans; P = .005) and to have body fluid cultures drawn. Latino infants also were more likely than African American infants to undergo chest radiography and respiratory virus rapid antigen testing (P ≤ .01). Latino infants from Spanish-speaking families had a higher rate of respiratory syncytial virus testing compared with those from English-speaking families (76% vs 51%; P = .016). CONCLUSION Providers caring for Latino infants with acute respiratory illness ordered more antibiotics and diagnostic testing for this group, particularly compared with African Americans, even though the 2 groups had similar disease severity and socioeconomic disparities. Language barrier may be a possible explanation for these differences.

Association between breast-feeding and severity of acute viral respiratory tract infection.

In a cross-sectional analysis of 629 mother-infants dyads, breast-feeding (ever vs. never) was associated with decreased relative odds of a lower versus upper respiratory tract infection (adjusted odds ratio: 0.64; 95% confidence interval: 0.42–0.99). There was not a significant association between breast-feeding and bronchiolitis severity score or length of hospital stay.