title: Age and gender-specific reference intervals for lysosomal enzymes in dried blood spot samples: A study in Indian population.
abstract: OBJECTIVE
  The study aimed to establish age and gender-specific reference values for the activities of lysosomal enzymes (acid α-galactosidase [GLA], acid β-glucocerebrosidase [GBA], acid α-glucosidase [GAA], acid sphingomyelinase [ASM] and galactocerebrosidase [GALC]) in dried blood spots (DBS) of Indian population.
  
  
  METHODS
  A total of 3797 healthy Indian subjects (1456 females and 2341 males) aged from 2days to 60years were selected for the study. Activities of 5 lysosomal enzymes were determined by tandem mass spectrometry, for newborns (<30days), infants (>1month-1year), children (>1-5years) and (>5-18years) and adults (>18years).Variations in enzyme activities based on age and gender were studied. The reference interval was defined as the central 95% range, and was determined based on age and gender.
  
  
  RESULTS
  Highly significant differences in activities were observed for GAA (p=0.001), GLA (p<0.0001), GBA (p<0.0001), ASM (p<0.0001) and GALC (p<0.0001), between different age groups. Comparison of activities between genders showed significant difference for ASM in children aged 1-5years (p=0.03) with higher activity in females, and for GLA in children aged 5-18years (p=0.004) where the activity was higher in males. Reference intervals decreased with age for all enzymes, except GAA. The ranges of GLA and GALC were higher in females, whereas GBA was higher in males.
  
  
  CONCLUSIONS
  The study establishes age and gender-specific reference values for the screening and identification of lysosomal storage disorders in Indian population. Our data may facilitate establishment of mass screening programs for these disorders in India.
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health and Neuro Sciences, Bangalore 560029, India.
authors.forename: Manjunath
authors.initials: M
authors.lastname: Supriya
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health and Neuro Sciences, Bangalore 560029, India.
authors.forename: Tanima
authors.initials: T
authors.lastname: De
authors.affiliation: Department of Neurochemistry, National Institute of Mental Health and Neuro Sciences, Bangalore 560029, India. Electronic address: rita@nimhans.ac.in.
authors.forename: Rita
authors.initials: R
authors.lastname: Christopher
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D059788:Dried Blood Spot Testing / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D007194:India; D007223:Infant; D007231:Infant, Newborn; D008247:Lysosomes / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D053719:Tandem Mass Spectrometry / Q000379:methods / Q000592:standards
keywords: Dried blood spot; Lysosomal enzymes; Reference range; Tandem mass spectrometry