title: Elevation of 1-hour plasma glucose during oral glucose tolerance testing is associated with worse pulmonary function in cystic fibrosis.
abstract: OBJECTIVE
  Cystic fibrosis (CF)-related diabetes (CFRD) is associated with declining pulmonary function and increased mortality. During oral glucose tolerance testing (OGTT), CFRD is defined by 2-h plasma glucose (PG2). We hypothesized PG elevations during OGTT resolving by 2 h, not meeting CFRD criteria, influence pulmonary function in CF. Thus we investigated the frequency of elevated 1-h OGTT PG (PG1) and its relationship with pulmonary function.
  
  
  METHODS
  Retrospective review of OGTTs was performed between August 2005 (annual screening initiation) and June 2008 at Children's Hospital of Philadelphia CF Center. First-time, well state OGTTs (PG0, PG1, PG2) were analyzed. Additional data collected were: percent predicted forced expiratory volume in 1 s (FEV(1)), BMI percentile, lung bacterial colonization, age, and sex. OGTTs were categorized as normal (PG2 <140 mg/dL), impaired glucose tolerance (IGT) (PG2 140-199 mg/dL), CFRD (PG2 ≥ 200 mg/dL), and indeterminate glycemia (INDET) (PG1 ≥ 200 mg/dL and PG2 <140 mg/dL). Frequency of PG1 ≥ 140 but <200 mg/dL was also noted. Multivariable linear regression was used to assess associations between percent predicted FEV(1), BMI percentile, and OGTT PG.
  
  
  RESULTS
  OGTTs (101) were available (59 male/42 female; age 5.8-22 years, percent predicted FEV(1) = 94.5 ± 18%, BMI percentile = 52 ± 25%). With the use of PG2, 91 OGTT were normal, eight were IGT, and two were CFRD. With the use of PG1 (n = 89), 39 OGTT were normal, 36 were PG1 ≥ 140 <200 mg/dL, and 14 were PG1 ≥ 200 mg/dL. PG1 was negatively associated with percent predicted FEV(1), adjusting for BMI percentile (P = 0.009, R(2) 0.13). Percent predicted FEV(1) was not associated with PG0, PG2, age, sex, or lung bacterial colonization.
  
  
  CONCLUSIONS
  PG elevations at nontraditional OGTT times are common in CF. The association of increasing PG1 with worse pulmonary function suggests early PG abnormalities may be deleterious or an early marker for worsening disease and will be missed if CFRD diagnosis focuses on PG2.
authors.affiliation: Division of Pediatric Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA. brodskyjl@chop.edu
authors.forename: Jill
authors.initials: J
authors.lastname: Brodsky
authors.forename: Shayne
authors.initials: S
authors.lastname: Dougherty
authors.forename: Ramkrishna
authors.initials: R
authors.lastname: Makani
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Rubenstein
authors.forename: Andrea
authors.initials: A
authors.lastname: Kelly
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D018149:Glucose Intolerance / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology; D005951:Glucose Tolerance Test; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D001786:Blood Glucose