title: Assessment of plasma chitotriosidase activity, CCL18/PARC concentration and NP-C suspicion index in the diagnosis of Niemann-Pick disease type C: a prospective observational study.
abstract: Niemann-Pick disease type C (NP-C) is a rare, autosomal recessive neurodegenerative disease caused by mutations in either the NPC1 or NPC2 genes. The diagnosis of NP-C remains challenging due to the non-specific, heterogeneous nature of signs/symptoms. This study assessed the utility of plasma chitotriosidase (ChT) and Chemokine (C-C motif) ligand 18 (CCL18)/pulmonary and activation-regulated chemokine (PARC) in conjunction with the NP-C suspicion index (NP-C SI) for guiding confirmatory laboratory testing in patients with suspected NP-C.
  
  
  
  In a prospective observational cohort study, incorporating a retrospective determination of NP-C SI scores, two different diagnostic approaches were applied in two separate groups of unrelated patients from 51 Spanish medical centers (n = 118 in both groups). From Jan 2010 to Apr 2012 (Period 1), patients with ≥2 clinical signs/symptoms of NP-C were considered 'suspected NP-C' cases, and NPC1/NPC2 sequencing, plasma chitotriosidase (ChT), CCL18/PARC and sphingomyelinase levels were assessed. Based on findings in Period 1, plasma ChT and CCL18/PARC, and NP-C SI prediction scores were determined in a second group of patients between May 2012 and Apr 2014 (Period 2), and NPC1 and NPC2 were sequenced only in those with elevated ChT and/or elevated CCL18/PARC and/or NP-C SI ≥70. Filipin staining and 7-ketocholesterol (7-KC) measurements were performed in all patients with NP-C gene mutations, where possible.
  
  
  
  In total across Periods 1 and 2, 10/236 (4%) patients had a confirmed diagnosis o NP-C based on gene sequencing (5/118 [4.2%] in each Period): all of these patients had two causal NPC1 mutations. Single mutant NPC1 alleles were detected in 8/236 (3%) patients, overall. Positive filipin staining results comprised three classical and five variant biochemical phenotypes. No NPC2 mutations were detected. All patients with NPC1 mutations had high ChT activity, high CCL18/PARC concentrations and/or NP-C SI scores ≥70. Plasma 7-KC was higher than control cut-off values in all patients with two NPC1 mutations, and in the majority of patients with single mutations. Family studies identified three further NP-C patients.
  
  
  
  This approach may be very useful for laboratories that do not have mass spectrometry facilities and therefore, they cannot use other NP-C biomarkers for diagnosis.
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain. isadco@gmail.com.|Instituto de Investigación Sanitaria Aragón (IIS Aragón), Saragossa, Spain. isadco@gmail.com.
authors.forename: Isabel
authors.initials: I
authors.lastname: De Castro-Orós
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.|Instituto de Investigación Sanitaria Aragón (IIS Aragón), Saragossa, Spain.|Centro de Investigación Biomédica en Red (CIBERER), Instituto de Salud Carlos III, Saragossa, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Irún
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.|Spanish Foundation for the Study and Therapy of Gaucher Disease, Saragossa, Spain.
authors.forename: Jorge Javier
authors.initials: JJ
authors.lastname: Cebolla
authors.affiliation: Centro de Investigación Biomédica en Red (CIBERER), Instituto de Salud Carlos III, Saragossa, Spain.|Biochemistry and Molecular Biology Research Centre for Nanomedicine, Vall d'Hebron University Hospital, Barcelona, Spain.
authors.forename: Victor
authors.initials: V
authors.lastname: Rodriguez-Sureda
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Mallén
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Pueyo
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Mozas
authors.affiliation: Centro de Investigación Biomédica en Red (CIBERER), Instituto de Salud Carlos III, Saragossa, Spain.|Biochemistry and Molecular Biology Research Centre for Nanomedicine, Vall d'Hebron University Hospital, Barcelona, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Dominguez
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Faculty of Science, University of Zaragoza, C. Pedro Cerbuna 12, 50009, Saragossa, Spain.|Instituto de Investigación Sanitaria Aragón (IIS Aragón), Saragossa, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Pocoví
mesh_terms: D000293:Adolescent; D000328:Adult; D019742:Chemokines, CC / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D003710:Demography; D005190:Family; D005260:Female; D005372:Filipin; D006596:Hexosaminidases / Q000097:blood*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009154:Mutation; D052556:Niemann-Pick Disease, Type C / Q000097:blood* / Q000175:diagnosis* / Q000201:enzymology; D000072376:Oxysterols; D011446:Prospective Studies; D055815:Young Adult
chemical_list: C111792:CCL18 protein, human; D019742:Chemokines, CC; D000072376:Oxysterols; D005372:Filipin; D006596:Hexosaminidases; C086400:chitotriosidase
keywords: 7-ketocholesterol; CCL18/PARC; Chitotriosidase; Diagnosis; NP-C suspicion index; Niemann-Pick disease type C; Screening