“The first three years of a child's life are a crucial time of development...and what happens during those years stays with a child for a lifetime.”

What is the best test to diagnose developmental delay in children under the age of six?

Developmental Delay is when a child does not reach developmental milestones at expected times in their life. It is an ongoing delay in the process of development occurring in one or many areas, (gross or fine motor, language, social, or thinking skills). Developmental delay can have many different causes, such as genetic causes (like Down syndrome), or complications of pregnancy and birth (like prematurity or infections). Most often, the specific cause is unknown. Some causes can be easily reversed if caught early enough, such as hearing loss from chronic ear infections, or lead poisoning.
Parents are usually the first to notice the child is not progressing at a normal rate. If the child seems behind, act early and talk with a pediatrician, they may use a set of screening tools to help diagnose any developmental delay. The sooner a delayed child gets intervention, the better progress will be.

Milestones to look for in child development:
4 frequently used screening tools for developmental delay in children 0-6 are listed below:
  1. Bayley III Bayley Scales of Infant and Toddler Development-Third Edition
  2. Denver II
  3. Peabody Developmental Motor Scales-2
  4. Zurich Neuromotor Assessment – Part 3

Summary Table


Age Group

What it tests

Bayley III
1 month to 3 1/2 years
Tests cognitive, language, motor, social-emotional and adaptive behavior by challenging the child with increasingly difficult tasks to determine developmental age.
Denver II
Birth to 6 years
Tests social/personal, fine motor function, language and gross motor functions by having the child demonstrate different tasks.
Peabody Developmental Motor Scales-2
Birth to 5 years
Tests gross and fine motor skills in order to compare the child to other children their age.
Zurich Neuromotor Assessment-Part 3
3 to 5 years
Tests fine and gross motor skills by complex tasks in order to identify if the child is within the normative range.

Bayley Scales of Infant and Toddler Development-Third Edition

The Bayley-III is designed for children of all ethnicities between the ages of 1 month and 3 ½ years, to identify developmental delay and delineate areas in which to begin intervention. It addresses cognitive, language, and social delays based on norm-referenced developmental timelines. The test takes between 50-90 minutes to complete, and is administered by a licensed professional that is familiar with the Standards for Educational and Psychological Testing.
Within the test are 5 distinct scales:
  • Cognitive
  • Language (expressive and receptive questions)
  • Motor (fine and gross motor tasks)
  • Social-emotional (questionnaire completed by the caregiver)
  • Adaptive behavior (questionnaire completed by the caregiver).

The Bayley-III is scored based on the completion of increasingly more “advanced” tasks, adjusted for prematurity if needed, then compared to norm-referenced scores. The normative sample does contain some children with diagnosed developmental delays to reflect a representative sample of the US population; however children not proficient in the English language were excluded in the sample. Included with the testing materials is information regarding how to adapt the test for children with physical or sensory disabilities. [1]

While some testing of the Bayley-III against healthy children has shown that the test may miss minor impairments, it is a widely utilized and rigorously tested measure that can be used to help detect impairments and retest for improvements in young children. The utilization of the developmental quotient as described in Milne et al. (developmental age/actual age x 100) may help to enhance the sensitivity of the test. [2]

This measure can be found/purchased at: Pearson Clinical:Bayley III Test
Frequently asked questions about test administration:FAQ

Denver II Developmental Screening Test

The Denver Developmental Screening Test is an assessment for examining the developmental progress of children. The scale is based on what percentage of a certain age is able to perform a certain task. This test was developed in 1967, and due to concerns about its reliability, a new test was made, The Denver II Developmental Screening Test in 1992. The Denver II Test has 20 additional questions mostly concerning expressive language and articulation skills. The age range for the Denver II is birth to six years, just as the original.
The arrangement of the Denver II includes 125 items organized into four subcategories:
  • Social/personal
  • Fine motor function
  • Language
  • Gross motor functions
Application of the test should be administered by a health care professional, teacher, or early childhood professional. The test takes approximately 20 minutes to administer and interpret. [3]

The Denver II stands out from other developmental screening tests for a number of reasons:
  • It bases its validity on a standardized norm of 2,000 children rather than on specificity and sensitivity
  • The test takes into account different subgroups such as race and sex
  • It is primarily based on reports from an actual observer and not just parental report
  • It contains a behavior rating scale.

A study was published in the Official Journal of the American Academy of Pediatrics concerning the accuracy of the Denver II in developmental screening. The study consisted of 104 children from five different day cares. The age range of the children tested was 3 to 72 months old. The results showed that most children with developmental problems, even those that were subtle, received abnormal scores on the Denver II. With this result, the test was found to have high sensitivity. However, the specificity was very low. It was found that there was a large amount of over referral. About three out of five children taking the test would be referred for evaluation, and less than one of the three referred would have true developmental problems. The researchers came to the conclusion that based upon the low specificity of the Denver II, further changes and development of the test were needed. They stated that until this test is revised, those conducting developmental screening tests should use those with high sensitivity as well as high specificity.[4]

This measure can be found/purchased at: Purchasing the Denver II
Frequently asked questions: FAQ

Peabody Developmental Motor Scales-2

The Peabody Developmental Motor Scales-2 tests is for diagnosing developmental delay in children ages birth to 5 years. It is a norm-referenced test, meaning that it tells you how the child compares to other children their age. The standard score of this test is 100 with a standard deviation of 15. Children are considered to have developmental delay if they are two standard deviations from their chronological age. The test should take between 45 to 60 minutes to administer.

The Peabody Developmental Motor Scales-2 test has six subscales split into two groups, gross and fine motor.
Gross Motor:
Reflexes (for children birth to 11 months)
Object manipulation (for children older than 12 months)
Fine Motor:
Visual-Motor Integration

Separate scores for fine and gross motor skills
Poor concurrent validity with other developmental tests
Multiple subscales for fine motor skills
Some evidence suggest that the Peabody Developmental Motor Scales-2 is not the best diagnostic test to diagnose developmental delay in early childhood. Provost et al. (2004) showed that the Bayley III Bayley Scales of Infant and Toddler Development-Third Edition and the Peabody do not have concurrent validity when diagnosing developmental delay. 75% of the time when the Bayley III showed that a child was eligible for support services because they had developmental delay, the Peabody did not show the that the child was eligible for services. With this evidence, the Bayley III may be a better diagnostic test for developmental delay.[5]

This measure can be found/purchased at:
Pearson Clinical: Peabody Test

Zurich Neuromotor Assessment – Part 3

The Zurich Neuromotor Assessment (ZNA) was originally developed as a neurodevelopment approach to describe motor development from school age to adolescence. The ZNA was created to take into account the large variability between children, but was not originally designed for children younger than 5 years of age. The ZNA was modified to extend to children 3-5 years old (ZNA3-5). The ZNA3-5 is adapted (fewer repetitions) and modified for children 3-5 years old and contains essentially the same items used as the original ZNA that involved children 5-18 years of age (ZNA5-18).

The ZNA3-5 is a standardized procedure for assessing speed of motor tasks and the quality of movement.

ZNA3-5 was a cross-sectional study involving 101 children that were enrolled in day-care centers in Zurich, Switzerland. Only typically medical, behavioral, and physical developing children were included in the study. The institutional review board of Canton Zurich approved the study. ZNA3-5 provides normative values for fine and gross motors skills in typically developing children 3-5 years of age. Previously, there was no data giving particular attention to typical movements and variability, only deficiencies. Can be used for differential examination of children with neurological disturbances (cerebral palsy).

To study fine motor movements the materials from ZNA5-18 were used in addition to a pegboard task, stringing beads task, and a turning bolts task.
To assess gross motor skills the Bayley stairs were used, a wooden board for balance testing, a bright sign for participants to run around, and an elastic band for assessing ability to walk in a straight line.

The assessment includes:
- Pegboard with 12 holes
- Stringing of 6 beads
- Turning a bolt
- Repetitive, alternating, and sequential movements (heel taps, hand taps, alternating supination/pronation, tapping of fingers, opposing finger to thumb)
- Static/dynamic balance

Total test time = 20 minutes

Evidence Cont'd: Reliability of timed performance measurements was greater (0.95, 0.0, and 0.65) than associated movement ratings (0.8, 0.7, and 0.4).

*All tests were evaluated with both dominant and non-dominant sides.
*All performances were rated on a five-point ordinal scale (from 0=excellent to 4=unable) or was a timed task
*The ZNA3-5 presents normative values of gross and fine motor skills in typically developing school children under the age of 5 years old.
*ZNA3-5 provides diagnostic criteria for development coordination disorder (DCD) at the earliest stages taking into account the high variability in children this age.[7]

*Early identification of motor deficiencies can prevent more serious motor delay in the future

Clinical Relevance:
-Assess movement performance
-Assess movement quality (contralateral associated movements)
-Research version: expresses findings of exam in percentiles and z-scores/provides printed analyzed results

This measure can be found/purchased at:


After reviewing the four tests above, we have noticed multiple differences that make them better for different scenarios. The Bayley III is best for ages 1 month to 42 months. The advantages of this test are it is based on a normative sample, strong internal consistency and describes accommodations for physically or sensory impaired children. The Denver II has a wide age range from birth to 6 years and is very sensitive but not very specific. One advantage of this test is that it takes into account different subgroups such as race and sex. The Peabody 2 is for children from birth to 5 years. This test separates fine and gross motor skills but does not have high concurrent validity with other developmental delay tests. The ZNA3-5 is for children ages 3 to 5 years old. It is best for evaluating the neuromotor developmental status of a child. This highly reliable test provides normative data for gross and fine motor tasks in children.

Overall, we have determined that the Bayley III is the preferred method of diagnosing developmental delay in children under 6 years old. We believe this because it is highly sensitive compared to the other tests described, meaning that it is unlikely to miss a developmental delay when a child has one. It also has high concurrent validity with other developmental delay tests. However, if the healthcare provider administering the test or the parents feel like there is a missed diagnosis then we recommend they administer another test and talk to their doctor.
  1. ^

    Kolobe, T. Bayley Scales of Infant and Toddler Development- Third Edition (Bayley-III)
    Published 2010. Accessed March 8, 2014.
  2. ^

    Milne S, Mcdonald J, Comino EJ. The Use of the Bayley Scales of Infant and Toddler Development III with Clinical Populations: A Preliminary Exploration.
    Phys Occup Ther Pediatr.32(1):24–33. doi: 10.3109/01942638.2011.592572
  3. ^

    Willacy H. Denver Developmental Screening Test. PatientPlus Database. Published 2010. Reviewed 2014. Accessed March 6, 2014
  4. ^

    Glascoe FP, Byrne KE, Ashford LG, Johnson KL, Chang B, Strickland B. Accuracy of the Denver-II in Developmental Screening.
    Pediatrics. 1992; 89(6 pt 2): 1221-225. Accessed March 6, 2014.
  5. ^

    Provost B, Heimerl S, McClain C, Kim NH, Lopez BR, Kodituwakku P. Concurrent validity of the Bayley Scales of Infant Development II Motor Scale
    and the Peabody Developmental Motor Scales-2 in children with Developmental Delays. Pediatr Phys Ther. 2004; 16, 149-156. Accessed March 6, 2014
  6. ^

    Kakebeeke T, Caflisch J, Chaouch A. Neuromotor development in children. Part 3: motor performance in 3-to 5-year-olds. Dev Med Child Neurol. 2013;
    55 (1): 248–256. doi: 10.1111/dmcn.12034
  7. ^

    Gasser T, Rousson V, Caflisch J, Jenni OG. Development of motor speed and associated movements from 5 to 18 years. Dev Med Child Neurol. 2010;
    52 (1): 256-263. doi: 10.1111/j.1469-8749.2009.03391.x