The number of referrals under strict adherence to the Dutch consensus guidelines for short stature was estimated using longitudinal data from 970 children (0–10 years). Results showed that over 38% of all children would have to be referred one or more times. There is therefore a clear need to revise the current guidelines.
- height velocity
- short stature
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A few years ago the Dutch Institute for Health Care Improvement published Consensus Guidelines for promoting early diagnosis and treatment of short stature.1 It was expected that use of these guidelines would lead to approximately 2500 referrals per year from the regular child health care system to a paediatrician. There was, however, little evidence that could back up this estimate.
PARTICIPANTS, METHODS, AND RESULTS
The guidelines introduced six screening rules based on height standard deviation scores (HSDS). Boys younger than 10 years and girls younger than 9 years ought to be referred if:
HSDS is lower than −2.5
HSDS is lower than −1.3 and HSDS is 1.3 lower than the target height SDS
The growth curve deflects by more than 0.25 SDS per year
HSDS decreases by more than 1 SDS over several years
In children born small for dates (birth length SDS lower than −1.88) HSDS is lower than −1.88 after the age of 2
HSDS is lower than −1.3 and the child has disproportion or dysmorphic features.
Table 1 provides the precise description and the age range of each rule. These rules should be checked at each visit. A child should be referred if one or more rules are met.
We obtained longitudinal height data of the cohort of all children born in the years 1989 and 1990 in Landgraaf and Kerkrade, located in the southern part of the Netherlands (481 boys, 489 girls). The total number of recorded time points between 1989 and 2001 was 14 310. The mean SDS with respect to Dutch height reference was −0.31, consistent with known regional differences.2 In order to adjust for this, a constant of 0.31 was added to all height SDS scores. We coded all screening rules into a computer program, applied this program to the data, and calculated the percentage of children that should be referred under each rule.
Table 1 contains the results for rules I–V. No data were available for rule VI. About 6.2% of all Dutch children have a height SDS <−2.5 at one or more occasions between birth and 10 (boys) or 9 (girls) years. The estimated referral percentages are very high, especially for rule III (31.5%). Combining rules I–V results in 38.2% referrals in total. The guidelines are ambiguous as to whether rules II and III should start at birth or at age 3 (as in table 1). A start at birth results in even more dramatic referral percentages: from 5.9% to 24.4% for rule II, and from 31.5% to 84.6%(!) for rule III.
Strict application of the guidelines would lead to an overwhelmingly large number of false positives, would seriously impair regular practice, and create avoidable anxiety. The high referral percentages are remarkable. By definition, under rule I only 0.4% of the children have an HSDS <−2.5 at a given time point, whereas the estimated percentage is 6.2%. These differences might be due to repeated testing and unaccounted variability. Infant length is measured about 10 times during the first two years of life. Infants are notoriously difficult to measure accurately. Variability in this period is large, and so the probability that a child has at least one HSDS <−2.5 is considerably larger than 0.4%. In addition, the referral criteria do not account for differences in gestation, so premature births form a relatively large proportion of children short at birth. When rule I is started at age 2 instead of birth, it refers to only 0.8% of the children, which is much closer to what could be expected on theoretical grounds.
A referral percentage of 38.2% corresponds to approximately 77 000 children in the Netherlands each year. This is over 30 times the number expected by the consensus committee. We recommend a revision of the current screening criteria, where the development of more stringent rules is based on adequate empirical evidence.