**14 October 2020**: Articles

# Limitations of Dutch Growth Research Foundation Commercial Software Weight Velocity for Age Standard Deviation Score

Rare disease

*Martin J.C. Van Gemert*

^{1ABCDEF*},

*Marianne Vlaming*

^{2ABDEF},

*Bülent Köseoğlu*

^{3ABCD},

*Cornelis M.A. Bruijninckx*

^{4ABCDE},

*Ton G. Van Leeuwen*

^{1ACDE},

*Martino H.A. Neumann*

^{5ACDEF},

*Pieter J.J. Sauer*

^{6ABCDE}

DOI: 10.12659/AJCR.925551

Am J Case Rep 2020; 21:e925551

## Abstract

**BACKGROUND:** The commercial software for hospitals, *Weight Velocity for Age Standard Deviation Score *(*SDSWVA*), claims to document the growth and development of children, although published details are unavailable. The statistics-derived parameter *SDSWVA* includes the *weight velocity* at age *t*, *WV(t)* (weight gained between *t* and (*t*–1.23) years, divided by 1.23), and 3 standard weight velocity curves at average age *AA*, defined as *AA*=*t*–1.23/2 years. *SDSWVA *denotes the number of standard deviations that *WV(t)* deviates from the *0 SD* weight velocity at *AA*. *WV(t)* yielded erroneous outcomes when applied to weights of a seriously underweight boy with an allergy to cows’ milk who showed strong weight growth after being fed on food free of cows’ milk. The *SDSWVA *software tacitly suggests that it is more accurate than *WV(t)*.

**CASE REPORT:** The case of this boy was previously described in this Journal. Using *SDSWVA(t,AA)* software, his weight growth was analyzed by his third pediatrician, beginning at age 1.5 years. The diagnosis of the mother with Pediatric Condition Falsification was confirmed, adding 6 months to foster care, which totalled 8.5 months. Testing of the *SDSWVA *software on the boy’s weight curve yielded results that were complex, nontransparent, and as erroneous as *WV(t)*, explaining the misdiagnosis by the third pediatrician.

**CONCLUSIONS:** *SDSWVA *software should not be used for children under 3 years and during variable weight behavior. Erroneous performance, unpublished details, and an error identified in their new but untested software make the Dutch Growth Research Foundation unlikely to meet the 2020 European Union regulations for *in vitro* medical devices.

**Keywords:**
Body Weight Changes, case reports, Diagnostic Errors, Software, Child, Child, Preschool, Infant

### Background

The

We previously showed that

In the Appendix below we explain how the

### Case Report

**EARLIER:**

The erroneous behavior of WV(t) was evident when applied to the weight curve of an infant boy [1]. Figure 1 shows his weight curve at 15 consecutive age periods (see Schematic Model below). Briefly [3], the boy was born at 39 gestational weeks as the sixth child of normal parents, weighting 3.18 kg. He was hospitalized for 2 weeks during age period 2 because of a slightly negative weight gain. Allergy to cows’ milk was suspected, with subsequent removal of cows’ milk from his diet resulted in a rapid weight gain (periods 3 and 4). Despite impressive weight growth, during periods 3–11 (age 0.33–2.4 years), which was 1.3- to 2.3-fold greater than the corresponding weight growth on the 0 SD standard weight curve, his first pediatrician stated in a legal summary of the second of 3 juvenile court hearings held in the boy’s case that “the boy does not grow” and ordered his mother to increase his food intake stepwise to 3.5 times normal (period 8) [3]. During period 8 (period 6 of [3]), the boy’s weight velocity was 2.1 times the 0 SD weight velocity. This pediatrician, as well as the second pediatrician, who was willing to confirm all the erroneous statements made by the first pediatrician during the second juvenile court hearing, appeared unable to distinguish (low) weight from (exceptional) weight growth [3]. Based on these reports, the mother was diagnosed with PCF and the boy was placed in foster care for 8.5 months.

**CASE REPORT:**

The present case begins during period 10, after the boy was in foster care for 2.5 months, at the time his third pediatrician was appointed. This pediatrician analyzed his weight growth with

SDS(t) and SDSSM(t,AA) were applied to 2 weight curves of this boy (Figure 1). The first weight curve (the clinical weights) was of the actual measured weights of the boy until age 3.1 years [1,3], whereas the second weight curve, the Schematic Model of his weights [1], replaced the individually measured weights with weights clustered in 15 consecutive age periods by least-squares fitting. The virtually linear increase in weight in all age periods gave 15 individual but accurate Period-Averaged-Weight-Velocities (Table 1 in [1], summarized in the caption to Figure 1). For comparison we also show the 0 SD standard weight curve.

We calculated (a) SDSWVA(t,AA), the Weight Velocity for Age Standard Deviation Score of the boy’s clinical weights, and (b) SDSSM(t,AA), the Weight Velocity for Age Standard Deviation Score of the Schematic Model [1] with their exact Period-Averaged-Weight-Velocities, but including average age AA. We compared these 2 predictions with (c) SDSSM(t), the exact Standard Deviation Score of the Schematic Model with Period-Averaged-Weight-Velocities but without AA, here considered the standard for SDS-calculations, as these are arguably the most exact approximations of real weight growth velocity. The Table 1 summarizes the 3 case examples. This approach shows the effects on SDS-calculations of natural weight fluctuations, the 1.23 years of inter-weight age interval for WV, and the use of an average age AA.

### Results

Figure 1 shows that, when the boy’s life became normal again, the

### Discussion

This study showed that the software package of the

The key finding of this study was that the

Erroneous outcomes of

Additionally, we purchased version

### Conclusions

The

### Figures

**Figure 1..**

*Clinical weights (blue open circles) [1,3]; Schematic Model weight curve with 15 consecutive age periods (red points), age periods indicated with blue labels on horizontal axis [1]; and 0 SD standard weight curve (black line) [5]. Each age period and corresponding Period-Averaged-Weight-Velocity (period; PAWV in kg/year) are: (1;5.7), (2;–1.14), (3;17.1), (4;5.5), (5;–9.5), (6;7.5), (7;–25.5), (8;6.2), (9;45.0), (10;3.55), (11;5.12), (12;–1.31), (13;1.02), (14;10.6), and (15;1.36).*

**Figure 2..**

*(a)SDSWVA(t,AA), Weight Velocity for Age Standard Deviation Score of the clinical weights (blue dots); (b) SDSSM(t,AA), Weight Velocity for Age Standard Deviation Score of the Schematic Model, with average age AA included but using the Period-Averaged-Weight-Velocity for each of the 15 periods (red dashed lines); and (c) SDSSM(t) of the Schematic Model using the Period-Averaged-Weight-Velocity for each of the 15 periods but not AA as the reference standard (solid red dashed lines). The Table 1 summarizes the description of the 3 cases.*

**Figure 3..**

*Weight Velocities of the +1 SD, 0 SD and −1 SD standard weight curves for Dutch boys [5]. The weight velocity data point at t1=1.42 years was set at WV(t1)=7 kg/year. In the first example (red lines below/right), the Standard Deviation Score at age t1 was SDS(t1=1.42)=X/Y=3.5 (Eq. 2a), indicating that the weight velocity at t1=1.42 years was 3.5 Standard Deviations above the mean of the data set, the 0 SD weight velocity at age t1. In the second example (red dashed lines middle), the SDSWVA(t1,AA)=A/B=1.56 (Eq. 4a), with the weight velocity at age t1=1.42 years being 1.56 Standard Deviations above the mean of the data set, the 0 SD weight velocity at average age AA=0.805 years.*

### References:

1.. van Gemert MJC, Bruijninckx CMA, van Leeuwen TG, Limitations of weight velocity analysis by commercial computer program Growth Analyser Viewer Edition: Ann Biomed Eng, 2019; 47(1); 297-305

2.. Ernst M, Bernhardt M, Bechstein M, Performance of semiautomatic assessment of carotid artery stenosis on CT angiography: Clarification of differences with manual assessment. Effect of CAD on performance in ASPECTS reading: Inform Med Unlocked, 2020; 18; 100295

3.. van Gemert MJC, Vlaming M, Osinga E, Pediatric condition falsification misdiagnosed by misjudged weight growth from the curve of measured weights: Am J Case Rep, 2018; 19; 752-56

4.. van Gemert MJC, Bruijninckx CMA, Neumann HAM, Weight velocity equations with 14–448 days time separated weights should not be used for infants under 3 years of age: Med Hypotheses, 2019; 129; 109234

5.. Gerver WJM, de Bruin R: Paediatric morphometrics, 2001, Maastricht, University Press Maastricht

## Figures

**Figure 1..**

*Clinical weights (blue open circles) [1,3]; Schematic Model weight curve with 15 consecutive age periods (red points), age periods indicated with blue labels on horizontal axis [1]; and 0 SD standard weight curve (black line) [5]. Each age period and corresponding Period-Averaged-Weight-Velocity (period; PAWV in kg/year) are: (1;5.7), (2;–1.14), (3;17.1), (4;5.5), (5;–9.5), (6;7.5), (7;–25.5), (8;6.2), (9;45.0), (10;3.55), (11;5.12), (12;–1.31), (13;1.02), (14;10.6), and (15;1.36).*

**Figure 2..**

*(a)SDSWVA(t,AA), Weight Velocity for Age Standard Deviation Score of the clinical weights (blue dots); (b) SDSSM(t,AA), Weight Velocity for Age Standard Deviation Score of the Schematic Model, with average age AA included but using the Period-Averaged-Weight-Velocity for each of the 15 periods (red dashed lines); and (c) SDSSM(t) of the Schematic Model using the Period-Averaged-Weight-Velocity for each of the 15 periods but not AA as the reference standard (solid red dashed lines). The Table 1 summarizes the description of the 3 cases.*

**Figure 3..**

*Weight Velocities of the +1 SD, 0 SD and −1 SD standard weight curves for Dutch boys [5]. The weight velocity data point at t1=1.42 years was set at WV(t1)=7 kg/year. In the first example (red lines below/right), the Standard Deviation Score at age t1 was SDS(t1=1.42)=X/Y=3.5 (Eq. 2a), indicating that the weight velocity at t1=1.42 years was 3.5 Standard Deviations above the mean of the data set, the 0 SD weight velocity at age t1. In the second example (red dashed lines middle), the SDSWVA(t1,AA)=A/B=1.56 (Eq. 4a), with the weight velocity at age t1=1.42 years being 1.56 Standard Deviations above the mean of the data set, the 0 SD weight velocity at average age AA=0.805 years.*

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