Three of 27 child health clinics had good routines in accordance
with the recommendations, where the baby scales were tested a
minimum of twice a year with a 5 kg weight. The “Midwife Home
Visitor” service also had good routines, where the scales
were regularly checked when serviced. Five child health clinics had
routines where they regularly tested the baby scales with weights
under 5 kg. For instance, they used weights of 0.5 to 1 kg, toys,
large liquid soap containers, loose-leaf binders and packages of
butter. The other child health clinics had no regular control
routines for baby scales, and none of the child health clinics had
routines for testing flat scales. The child health clinics that had
good routines and the “Midwife Home Visitor” service
had more accurate scales than the child health clinics that had no
routines, or had routines where they tested the scales with weights
under 5 kg.
Our results showed that even though many scales are highly
accurate, a scale that is not tested can in principle show any
reading. Only 16 of 152 scales showed 100 per cent correct weight.
Schlegel-Pratt and Heizer (4) believe that established standards
are important for accurate scales. It is conceivable that a
standard of 100 per cent correct weight is somewhat strict, but it
is difficult to judge acceptable deviations. Two different scales
used at the same child health clinic can be imprecise in either
direction, and can thus yield a wider discrepancy. This can result
in weight loss at one visit and weight gain at another visit, and
vice versa. Such weight variations can potentially affect decisions
with respect to interventions. A deviation of only 20 grams on a
baby scale can produce a discrepancy of 40 grams, and the larger
the deviation, the greater the potential consequences.
Consequences for practice
It is very important to assess weight development during the
neonatal period because weight reflects nutrition and well-being.
Difficulty with breastfeeding is the main reason for large weight
loss after birth (14). In newborns, a 10 per cent weight loss limit
has been established for implementing interventions (1). We saw
scales used for home visits that showed up to 590 grams too little
at 5 kg (Table 1), a deviation of more than 10 per cent. It is
conceivable that inaccurate scales can trigger interventions on a
completely erroneous basis. Such instances require public health
nurses to invest time and resources and can also have negative
consequences for the family concerned. For example, already
well-established breastfeeding may be disrupted if the mother loses
confidence in her ability to breastfeed.
A scale that is not tested can in principle show any
We also saw scales that showed up to 140 grams too much at 5 kg
(Table 1). Such a deviation can cause serious consequences in cases
where a mother is assured that her newborn has gained the normal
amount of weight, when in reality this may not be the case.
Collection of reliable weight measurements is usually not an
isolated act, but must be viewed in the context of an overall
assessment of the child (15). The clinical eye must therefore never
be underestimated. Looking at clinical signs in conjunction with
assessing the child's general condition provides valuable
additional information (1). It can be the most important background
for the decisions that are taken in cases where the scales do not
After babyhood, the child will be weighed at ages two and four.
The measuring point at age four is particularly important for being
able to determine early development of child overweight/obesity
(1). Public health nurses have a particular responsibility for
tracking a child's weight and recognising risk factors for
overweight/obesity and metabolic disorders (16). Earlier studies
have shown that inaccurate scales can lead to miscalculations of a
child's BMI (5, 6). It is essential that the scales measure
correctly if public health nurses are to prevent overweight/obesity
and implement individual interventions.
Control routines and standards for use
According to the weighing and measuring guidelines for the child
health clinic and school health services, growth measurements are
the surest method for assessing whether children are growing
satisfactorily (1). In view of this we question why the same
requirements are not made of the scales used in the public health
nurse service, as are made at GP surgeries and hospitals (8).
Today, it may appear that random circumstances and finances
determine the type of scale that is used. While public health
nurses do not diagnose and provide medical treatment, they perform
health monitoring at the individual and population level by
Since the results show significant differences in accuracy when
medically approved and non-medically approved scales are compared,
is it far from sufficient to perform health examinations with
scales that are not subject to requirements. A standard should
therefore also be introduced for the use of medically approved
scales in the child health clinic and school health services. WHO
recommends that bathroom scales should not be used in assessing a
child's growth since they have often proven to be unreliable
(17). This bolsters our recommendations to use medically approved
It is conceivable that inaccurate scales can trigger
interventions on a completely erroneous basis.
Control routines at child health clinics vary considerably. Few
child health clinics tested the scales in accordance with the
guidelines, and no child health clinics had routines for testing
flat scales. Minor deviations were found while testing 2 kg, but at
5 kg and above the deviations were considerable. Our results showed
reduced precision with increasing weight, particularly for
non-medically approved scales. These findings are in line with
Stein et al. (3), who also report that the scales show reduced
precision with increasing weight, and that control routines are
important for accuracy. Testing the scales with, for instance, 0.5
kg will give a false sense of security that the scales are
Schlegel-Pratt and Heizer (4) recommend regular tests with
certified weights. For this reason the child health clinics should
at least have 5 and 10 kg weights. In this way, systematic tests of
both baby and flat scales can be performed with 5, 10 and 15 kg,
and more deviations can be discovered. While procurement of weights
may be a question of finances, such an investment is a one-off
expense that will contribute to greater quality assurance in the
public health nurse service.
Transferability to the school health services
In this clinical audit we tested the scales at child health
clinics, but we believe that the results can also be transferred to
the school health services. The study conducted by Biehl et al.
(5), which was performed on scales at various schools, points out
that failure to test the scales will likely lead to miscalculations
of overweight and obesity. This finding is supported by Gerner et
al. (6), who state that inaccurate scales can lead to
miscalculations of children’s BMI. In the school health
services, children are weighed in the first, third and eighth grade
(2). During 40 kg tests, the maximum weight we tested, there was a
discrepancy of three and a half kilograms between the lowest and
highest measured weight (Table 1). It is conceivable that the
deviation will increase with higher weight. An eighth grader can
weigh more than 40 kg. Scales in the school health services should
therefore be tested with heavier weights, which can be a challenge
in terms of procurement and storage. One possibility is to consider
a service agreement with a calibration firm.
Strengths and weaknesses
One advantage of the audit was that all data were collected
directly at the child health clinics, with no use of
intermediaries. Accuracy was thoroughly tested by checking several
weights. We also tested repeatability and stability. We recorded
the type of scales that were used and could therefore compare
results from medically approved and non-medically approved scales.
We found few studies about the accuracy of scales through
systematic searches for scientific articles and no studies
concerning the accuracy of baby scales. Not recording the year in
which the various scales were put into service may constitute a
weakness, but it was difficult to obtain this information.
Public health nurses have a particular responsibility for
tracking a child's weight and recognising risk factors for
overweight/obesity and metabolic disorders.
According to Biehl et al. (5), newly procured scales usually
measure the correct weight. However, heavy use, incorrect use,
general wear and tear, and wear and tear due to frequent transport
affect accuracy. A common misunderstanding is that when a scale has
been installed and calibrated, instrument error is insignificant
(4). The scales at child health clinics are frequently used and are
moved in connection with home visits. Combined with the lack of
control routines, these factors entail a risk that the scales used
at child health clinics measure inaccurately. The study conducted
by Stein et al. (3) showed a level of inaccuracy that was three
times higher with worn scales than with scales in perfect
The final step in a clinical audit process involves implementing
measures in practice and conducting a new survey. Data collection
per se has no impact unless it is followed up (18). All of the
child health clinics received verbal or written feedback about the
results of their scales. Conducting this clinical audit heightened
awareness of the necessity of testing the scales at child health
clinics. Routines must be improved before a new survey can be
conducted. A good start would be for all child health clinics to
begin following the weighing and measuring guidelines for the child
health clinic and school health services by testing the scales a
minimum of twice a year. Furthermore, the tests must be conducted
with a weight the scale is meant to measure.
This audit, which was conducted on scales in use at child health
clinics and during home visits, showed that only nine of 102 (8.8
per cent) baby scales and seven of 50 (14 per cent) flat scales
were 100 per cent correct. There were also significant differences
in accuracy between medically approved and non-medically approved
scales. Only three of 27 (11.1 per cent) child health clinics had
good control routines for their scales. Our results thus show that
there is a discrepancy between practice and evidence-based
Measuring weight is a cost-effective and simple way of gathering
data about the population, but the validity of the measurements
must be critically assessed. Although the importance of weight
measurements is well documented, it appears that there may be a
lack of awareness about checking whether the scales actually
measure accurately. Ensuring good control routines and introducing
standards to use medically approved scales can help to quality
assure a valid collection of data in the child health clinic and
school health services.
Many thanks to all who made it possible to conduct the study:
Jörg Aßmus for helpful guidance in statistics, Evelyn Kvamme for
briefing us on weight calibration, and Petur Júlíusson and Jan
Larsen for lending certified weights.
Helsedirektoratet. Nasjonale faglige retningslinjer for veiing og
måling i helsestasjons- og skolehelsetjenesten. Oslo:
Helsedirektoratet. 2011. Available at:
https://helsedirektoratet.no/Lists/Publikasjoner/Attachments/236/Nasjonal-faglig-retningslinje-for-veiing-ogmaling-IS-1736.pdf (downloaded 20.04.
2. Sosial- og
helsedirektoratet. Kommunens helsefremmende og forebyggende arbeid
i helsestasjons- og skolehelsetjenesten. Oslo: Sosial- og
helsedirektoratet. 2004. Available at:
https://helsedirektoratet.no/Lists/Publikasjoner/Attachments/388/veileder-til-forskrift-kommunens-helsefremmende-og-forebyggende-arbeid-i-helsestasjons--og-skolehelsetj-.pdf (downloaded 20.04.
3. Stein RJ,
Haddock CK, Poston WS, Catanese D, Spertus JA. Precision in
weigting: a comparison of scales found in physician offices,
fitness centers, and weight loss centers. Public Health Rep.
2005;120:266–70. Available at:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1497726/pdf/16134566.pdf (downloaded 20.04.2016).
Schlegel-Pratt K, Heizer WD. The accuracy of scales used to weigh
patients. Nutr Clin Pract. 1990 Des 5(6):254–7.
5. Biehl, A,
Hovengen R, Meyer HE, Hjelmesæth J, Meisfjord J, Grøholt EK et al.
Impact of instrument error on the estimated prevalence of
overweight and obesity in population-based surveys. BMC Public
Health 2013;13:146. Available at:
http://www.biomedcentral.com/1471-2458/13/146 (downloaded 20.04.2016).
6. Gerner B,
Maccallum Z, Sheehan J, Harris C, Wake M. Are general practitioners
equipped to detect child overweight/obesity? Survey and audit. J
Pediatr Child Health. 2006;42(4):206–11.
7. Júlíusson PB,
Vinsjansen S, Nilsen B, Sælensminde H, Vågset R, Eide GE et al.
Måling av vekst og vekt: En oversikt over anbefalte teknikker.
Pediatrisk Endokrinologi 2005;19:23–9.
Forskrift om krav til ikke-automatiske vekter. 21. desember 2007
nr. 1527. Available at:
https://lovdata.no/dokument/SF/forskrift/2007-12-21-1735 (downloaded 20.04.2016).
Kunnskapsbasert praksis. Oslo: Nasjonalt kunnskapssenter for
helsetjenesten. 2004. Available at:
http://www.kunnskapssenteret.no/kunnskapsbasert-helsetjeneste/kunnskapsbasert-helsetjeneste (downloaded 19.05.2015).
10. Nortvedt MW, Jamtvedt G,
Graverholt B, Nordheim LV, Reinar LM. Jobb kunnskapsbasert! En
arbeidsbok. 2 ed. Oslo: Akribe. 2012.
Nasjonal strategi for kvalitetsforbedring i sosial- og
helsetjenesten … Og bedre skal det bli (2005–2015).
Oslo: Helsedirektoratet. 2005. Available at:
https://helsedirektoratet.no/Lists/Publikasjoner/Attachments/233/Og-bedre-skal-det-bli-nasjonal-strategi-for-kvalitetsforbedring-i-sosial-og-helsetjenesten-2005-2015-IS-1162-bokmal.pdf (downloaded 20.04.
12. Anderson DG. ABC of
audit. Tees Valley: Vocational Training Scheme. 2012. Available at:
http://www.gp-training.net/training/tutorials/management/audit/audabc.htm (downloaded 19.05.2015).
13. Polit DF, Beck CT.
Nursing research: generating and assessing evidence for nursing
practice. 8. ed. Philadelphia: Wolters Kluwer Health. 2014.
14. Dewey KG, Nommsen-Rivers
LA, Heinig MJ, Cohen RJ. Risk factors for suboptimal infant
breastfeeding behavior, delayed onset of lactation, and excess
neonatal weight loss. Pediatrics 2003;112(3 Pt 1):607–19.
15. Royal college of
nursing. Standards for the weighing of infants, children and young
people in the acute health care setting. London: The Royal College
of Nursing. 2013. Available at:
https://www2.rcn.org.uk/__data/assets/pdf_file/0009/351972/003828.pdf (downloaded 20.04.2016).
Nasjonale faglige retningslinjer for forebygging, utredning og
behandling av overvekt og fedme hos barn og unge. Oslo:
Helsedirektoratet. 2010. Available at:
https://helsedirektoratet.no/Lists/Publikasjoner/Attachments/389/nasjonal-faglig-retningslinje-for-forebygging-utredning-og-behandling-av-overvekt-og-fedme-hos-barn-og-unge.pdf (downloaded 20.04.2016).
17. World Health
Organization. Training Course on Child Growth Assessment. Geneve:
WHO. 2008. Available at:
http://www.who.int/childgrowth/training/en (downloaded 20.04.2016).
18. Benjamin A. Audit: how
to do it in practice. BMJ 2008;336:1241–5.