Objective: Rare disease 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 Erroneous performance, unpublished details, and an error identified in their new but untested software make the Dutch Growth Research Foundation unlikely to meet the 2020 European Union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.