HMOX1 and incontinentia pigmenti: However, because this research included a very small number of cases, the clinical utility of serum HO-1 measurement has not been examined for each IP subtype (for each IIP and SIP); therefore, the ability of serum HO-1 to detect AEs in patients with each IP subtype was evaluated for the purpose of validation and to compare with the detectability to other biomarkers commonly used in clinical practice.