A cross sectional study was implemented on 1503normal Egyptian infants aged from birth up to 30 months at vaccination centers and well-baby clinics. The study was carried out in a time frame from January 2019 till January 2020 in Egypt. A minimal sample size is calculated based on a previous study aimed to develop a screening test for the assessment of the motor-mental development of infants by selecting items from the Bayley Scales of Infant Development (BSID),7 concluded that a routine use of our test is recommended for following the development of normal infants as well as for screening from the community infants with possibility of development delay. The latter must be referred for detailed testing on the full scales. Based on this study, a sample size of 1500 infants is the enough required sample to conduct the trial(50 infant per each month of age) assuming a significance level of 95% (α = 0.05), and statistical power (1 – β) of 80%.8–9
The sample size was calculated according to Charan and Biswas (2013).10Online Open Source Epidemiologic Statistics for Public Health was also used to confirm the calculation.11
A total number of 1600 infants were enrolled on our study; exclusion criteria were applied to 97 children leaving 1503 children as a final total sample to be included in the study. The selected infants were divided into 30 groups based on their chronological age. The sample per month ranges between 44 to58 infants. Workshop training was provided to field work team to explain the items of the checklist and how to interview with the parents/or guardians. A pilot study of 150 infantswas designed (five infants per month) to test all items of the developmental checklist on Egyptian infants and also to test and standardize the capabilities of the involved team before proceeding to the main data collection. A consent was obtained from parents/or guardians who were informed about the objective of the study, its benefits and the absence of any risk associated with the participation of their infants.Egyptian Developmental Screening Chart (EDSC) was developed in a chart format as BDST for ease of administration enough to fit the Egyptian culture.
Inclusion and Exclusion criteria: Inclusion criteria included;full term infants, age from birth up to 30 months, anthropometric measurements (weight, length and head circumference) within normal for age according to WHO growth charts.Exclusion criteria included; history of prematurity, hospital admission including neonatal intensive care unit (NICU), malnourished baby according to WHO (≤–2 standard deviation of weight to height), known chronic diseases (cardiac, hematological, chest or endocrinal diseases) and known developmental or physical disability.
Data collection
Socioeconomic and demographic factors were collected using Fahmy schedule for estimating socioeconomic standard in Egypt. 12Infants were examined for any developmental or physical disability. Weight and length were assessed by identical measuring equipment. Weight was measured by a digital balanced scale (Beurer model G 11, Germany) and lengthwas assessed bya recumbent baby length scale. This is followed by an interview to their parents/or guardians to complete the developmental checklist. The checklist items are 54items (22 motors and 32 mental), translated to Arabic and simplified to the parents/or guardians with their local expressions. The scores of checklist items passed by infants were analyzed and tabulated. 97% pass level of developmental score of infants was taken as a reference. Any infant's score lies below 97% pass level considered delayed. Developmental age (DA) can be calculated from EDSC by intersection of the horizontal level of the score with the 50% pass level curve. Moreover, Developmental Quotient (DQ) was calculated directly from the EDSC. The DQ summarizes how well or poor the infant performs in contrast to a large group of infants at the same age. It was calculated as:( DA /CA) x 100.13 A z-score chart for motor and mental development follows up was designed by calculating each age group achievement.
Data Analysis
Collected data were adequately processed by statistical package SPSS, version 21 for windows (SPSS Inc., Chicago, Illinois, USA). Data were described using minimum, maximum, mean and standard deviation. For that, categorical variables were described using absolute frequency and percentage attributes. Moreover, comparisons were carried out between two studied dependent normally distributed variables using the paired T-test. Additionally, z-scores were calculated for age groups individually. Microsoft Excel (Microsoft Office Professional) enabled us to generate polynomial trend line curves. An alpha level was set to 5% with a significance level of 95%, and a beta error was accepted for up to 20% with 80%statistical power. A Z-score was calculated for each age group at the following: –3,–2,–1, 0,1,2,3 equally in sequence the percentiles (0.2nd, 2.3rd, 16th, 50th, 84th, 97.7th, 99.8th respectively).14