Introduction:

Early detection of patients with inborn errors of metabolism (IEM) can improve their prognosis. Patients’ signs and symptoms are helpful in identifying IEM. The objective of this study was to evaluate the diagnostic capacity of hypotonia and hyperammonemia as indicators of IEM in newborns.

Material and methods:

Observational and retrospective study. A total of 74 newborns treated in the Neonatology area of the Hospital Infantil de Especialidades del Estado de Chihuahua were included. The patients had records of the characteristics of newborn muscle tone, determination of serum ammonia levels and the result of the expanded neonatal screening for metabolic disorders. The diagnostic capacity of the clinical data was based on sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).

Results:

Six newborns with different IEM were detected; thus, the prevalence was 8.1%. By IEM group, organic acidemias were the most frequent. Hyperammonemia as a diagnostic marker IEM resulted in a sensitivity of 100%, specificity of 91.2%, PPV of 50% and NPV of 100%; while the results for hypotonia were 100%, 52.9%, 15.7% and 100%, respectively.

Conclusions:

Hypotonia and particularly hyperammonemia can be considered useful clinical findings for early detection of IEM.

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