title: Critical evaluation of ninhydrin for monitoring surgical instrument decontamination.
abstract: BACKGROUND
  New Department of Health (England) Choice Framework for Local Policies and Procedures guidance (CFPP 0101) still states that ninhydrin can be used to check for efficient protein removal from surgical instruments processed in sterile services departments (SSDs).
  
  
  OBJECTIVE
  With the potential transfer of variant Creutzfeldt-Jakob disease (vCJD) via surgical procedures it is necessary to re-evaluate recommended methods for protein detection.
  
  
  METHODS
  This paper reports studies on the sensitivity and applicability of ninhydrin for detecting proteins in laboratories and SSDs. The efficiency of protein removal by swabbing was also evaluated.
  
  
  RESULTS
  Ninhydrin showed poor sensitivity toward proteins. Limits of detection for bovine serum albumin (BSA) in solution were 205 μg/mL compared with arginine 6 μg/mL. A commercial kit could detect neither rat brain homogenate nor BSA at <1000 μg protein pipetted directly into the vials. Swabbing with water-wetted rayon swabs was inefficient at removing protein (50 μg) from instruments (N = 6) with 32 ± 4% BSA and 61 ± 5% fibrinogen remaining bound. Swabs dipped in 0.5% detergent (Triton X-100) solution had slightly better removal efficiency with 20 ± 3% BSA and 24 ± 2.8% fibrinogen remaining.
  
  
  CONCLUSIONS
  Ninhydrin kits, currently used in SSDs, are ineffective at detecting residual proteins due not only to the insensitivity of ninhydrin towards proteins but also to the poor desorption of adhered proteins by swabbing. Overall ninhydrin, either as a laboratory reagent or as supplied in protein detection kits, does not provide sensitive detection of proteins and generates high numbers of false negatives when used in decontamination practices.
authors.affiliation: Bioanalysis, William Harvey Research Institute, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
authors.forename: N K
authors.initials: NK
authors.lastname: Nayuni
authors.forename: E
authors.initials: E
authors.lastname: Cloutman-Green
authors.forename: M
authors.initials: M
authors.lastname: Hollis
authors.forename: J
authors.initials: J
authors.lastname: Hartley
authors.forename: S
authors.initials: S
authors.lastname: Martin
authors.forename: D
authors.initials: D
authors.lastname: Perrett
mesh_terms: D000818:Animals; D002417:Cattle; D003666:Decontamination / Q000379:methods* / Q000592:standards*; D004739:England; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism*; D009555:Ninhydrin / Q000378:metabolism*; D011506:Proteins / Q000032:analysis*; D011786:Quality Control; D051381:Rats; D012680:Sensitivity and Specificity; D013525:Surgical Instruments
chemical_list: D007202:Indicators and Reagents; D011506:Proteins; D009555:Ninhydrin