Ma et al. BMC Public Health 2012, 12:568 http://www.biomedcentral.com/1471-2458/12/568 Recent studies focused primarily on analyzing the as- sociation of CS-ICFI with infant growth measured by length-for-age z score (LAZ). However, results were in- consistent, with some studies finding a positive associ- ation [5-7], whereas others did not [8]. Furthermore, some researchers [9] built a longitudinal ICFI (L-ICFI) with summary of the information from several CS-ICFIs, and found it can provide information about feeding in a long term and associated with LAZ. To our knowledge, the ICFI has so far been used mostly in the context of African and Latin American countries. Hence, it is important to validate the index in other regions with different socio-economic and cultural context. A previous cross-sectional survey of ICFI has been carried out in China’s rural areas and found the as- sociation between ICFI and WAZ and WLZ [6], how- ever, this is the first study among infants and young children in an affluent metropolitan city. The aim of our study is to assess the applicability of CS-ICFI to Chinese diets and to available data in a very different Asian context, and to further construct L-ICFI which summarizes the information from several repeated CS-ICFIs. At last, we evaluate the association between cross-sectional or longitudinal index and infant and child growth. Methods Study design and participants This study was conducted in downtown area of Shang- hai, Kongjiang community, which is a typical community in Shanghai. Kongjiang Community Health Center rou- tinely provides basic medical services to the local com- munity, including well-child checks for the community’s infants and young children. From November 2008 to April 2010, all 6-month-old infants and their parents or main caregivers entering the Kongjiang Community Health Center for a routine well- child check were invited to take part in this study. Eligibility criteria for infants included healthy singleton infants, 6-month-old (5- to 7- month-old), born between 37 and 42 weeks gestational age, with birth weight be- tween 2,500 to 4,000 g, with no metabolic or physical problems. 295 infants aged 5-7 mo met the eligibility criteria. Eighteen mothers refused to participate and a total of 277 infants and their parents or main caregivers were included in the study at baseline and followed every 6 months, revisited around 12-month-old (10- to14- month-old) and 18-month-old (16- to 20-month-old). Questions about the main caregiver’s education, mother’s pre-pregnancy weight and height, family income were included in the baseline questionnaire. Infants feeding practices and consumption of food groups during the week preceding each visit were also assessed with Page 2 of 9 questionnaires. Anthropometrics at each visit were mea- sured. There were 29 infants had incomplete data at Visit 2, of whom the main caregivers of 2 infants refused to complete the questionnaire due to a lack of time and 27 infants had missing information in the questionnaire. There were 68 infants had incomplete data at Visit 3, of whom the main caregivers of 21 infants refused to complete the questionnaire because of a lack of time or impatience and 47 infants had missing information in the questionnaire. Only infant with a complete questionnaire and anthropometric data set of 3 visits were included in analysis, leaving a total of 180 infants. Infants were en- rolled after parents or main caregivers provided informed consent. The study protocol was approved by the Ethics Committee of Xinhua Hospital, affiliated to Shanghai Jiao Tong University School of Medicine. Data collection The weight and length of infants at each visit were mea- sured using standardized procedures in community health center. Weight was measured using an electronic pediatric scale to the nearest 0.01 kg, and length was measured using a pediatric-length board with the infant in a recumbent position. LAZ, weight-for-age z scores (WAZ), weight-for-length z scores (WLZ) were calcu- lated according to the 2006 WHO Child Growth Stan- dards using the WHO Anthro 2009 software [10]. Underweight, stunting and wasting were defined as WAZ < -2, LAZ < -2, and WLZ < -2, respectively. Over- weight was defined as WLZ > +2. The information of infant feeding practices was obtained based on 24-h and 7-d food recalls through on-site face-to-face interviews with the parents or main caregivers by a trained clinical research assistant at each visit. Infants and child feeding index (ICFI) The cross sectional infants and child feeding index (CS- ICFI) was constructed on the basis of current feeding practice for infants and young children recommended by WHO [11,12], as well as the methods proposed by other studies [2-4] taking into account local characteristics. In our study, the CS-ICFI was defined for 3 different age groups: 6-month (5- to 7-month), 12-month (10- to 14-month), and 18-month (16- to 20-month), respect- ively. The following 5 variables were used in the index construction: breastfeeding, food consistency, feeding frequency, dietary diversity score (DDS), and food group frequency score (FGFS), which were attributed in a man- ner that reflected the age change over the study period. Table 1 lists variables and the scoring system used to create the CS-ICFI for the different age groups. In particular,