To the Editor,
I read with great interest the article by Hans et al (1) reporting
the results of the 2006 Neonatal Nutrition Survey. This survey aimed to
assess the nutritional practices in the neonatal intensive care units
throughout the United States. This study is certainly of interest but I
have several major concerns about the conclusions of the authors.
My first concern relates to the first conclusion which states that
the data reflect an increase knowledge about best nutritional practices
for preterm infants. This conclusion may be, in fact, completed flowed by
the low rate of answers (i.e., 23%). When a mail questionnaire is used as
the data collection device, response rate is a primary concern since an
inadequate response jeopardizes the randomness or representativeness of
the sample and thus the ability to estimate population values. It is well
known that survey non-response can bias samples (and therefore survey
data) by making the sample composition substantively different from the
target population. Bias, in this instance, refers to the difference
between the sampled units and the target population. The biasing effect of
non-response can be greater as the response rate drops and, therefore,
researchers should seek higher response rates to decrease the likelihood
of non-response bias. However, survey error resulting from non-response
will only occur when there are significant differences between respondents
and non-respondents. The problem for survey researchers is, therefore,
understanding when non-response will not cause survey error and when it
will introduce bias that will affect data reliability–that is, under which
conditions are respondents and non-respondents most likely to differ?
Unfortunately, the authors did not address the non-response issue
adequately in order to increase confidence in data quality despite several
methods are available (2). Therefore, in absence of more precise
information on the quality of the data, one might postulate that the
physicians interested in nutrition where more prone to answer the survey.
Therefore, the apparent increase in knowledge about best nutritional
practices for preterm infants may be a true statement but only for a
selected group of physicians.
My second concern relates to the presentation of the data themselves.
As an example, the data presented in Table 2 suggest that prescribed
parenteral protein for low-birth-weight infants are, nowadays, appropriate
and close to the recommendations. However, it clear from the table that
some physicians still 1) prescribe protein on day 1 at a much lower level
than recommended (i.e.; 0.5 g/kg.d), 2) increase protein intake at a low
rate (i.e.; 0.25 g/kg.d) and 3) have a target intake for protein lower
than recommended (i.e., 2.5 g/kg.d). It would have been of interest for
the reader to have the proportion of the physicians who prescribe below
the recommendations for each nutrient.
My third concern relates to the last conclusion of the authors which
states that the data also “suggest that the persistent extrauterine growth
failure of preterm infants is not attributable to a lack of best
nutritional practice knowledge and intention”. No data in this manuscript
support this conclusion and, if there is a major non-respondent bias, as
discussed above, this conclusion is likely to be inaccurate. Furthermore,
the data reported in this manuscript demonstrate that the smaller the
infant, the lower are the nutritional intakes. This is a major issue,
since the smallest infants have the highest nutritional requirements and
the highest rate of extrauterine growth retardation (3). It is therefore
likely that the persistent extrauterine growth failure of extremely low
birth weight infants is still attributable to a lack of best nutritional
practice knowledge and intention in this group of infants. Finally, the
only data on which the authors rely there statement are data published in
2003 (3) but collected in the 90s, which was somewhat before the most
recent nutritional recommendations. This highlights, however, the need for
more recent growth surveys in very-low-birth-weight infants.
As a comparison, we performed a similar survey in France also in 2006
(4). The response rate of the physicians from the level III units was 85%.
Our study confirms the improvement in the neonatologists’ understanding
and knowledge of the nutritional needs of preterm infants. In comparison
with recent guidelines for parenteral nutrition for preterm infants, our
results indicate that the majority of the neonatal departments are
familiar with target macronutrient and energy intakes, but that the time
of introduction and the rate of progression of macronutrients,
particularly proteins and lipids, are frequently lower than those defined
by the guidelines. Furthermore, our study demonstrated a marked
heterogeneity between neonatal units and, therefore, confirms the marked
difference between centers for the nutritional management of neonates.
In conclusion, we believe that large-scale publication of new
nutritional guidelines for the parenteral nutrition of neonates and
preterm infants as well as regular, specific training in the parenteral
nutrition of preterm infants are still needed and we are concern that the
apparent, but maybe not universal, increase knowledge about best
nutritional practices for preterm infants reported in the manuscript of
Hans et al (1) may annihilate the recognition of a need for a specific
training in neonatal nutrition.
References
1. Hans DM, Pylipow M, Long JD, Thureen PJ, Georgieff MK. Nutritional
practices in the neonatal intensive care unit: analysis of a 2006 neonatal
nutrition survey. Pediatrics. 2009 Jan;123(1):51-7.
2. Groves RM. Nonresponse rates and nonresponse bias in household surveys.
Public Opinion Quarterly 2006 70:646-675
3. Dusick AM, Poindexter BB, Ehrenkranz RA, Lemons JA. Growth failure in
the preterm infant: can we catch up? Semin Perinatol. 2003;27:302–310
4. Lapillonne A, Fellous L, Mokhtari M, Kermorvant-Duchemin E. Parenteral
nutrition objectives for very low birth weight infants: results of a
national survey. J Pediat Gastroenterol Nutr 2009;48:618–626.
Conflict of Interest:
None declared
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