title: Performance of an Optimized Paper-Based Test for Rapid Visual Measurement of Alanine Aminotransferase (ALT) in Fingerstick and Venipuncture Samples.
abstract: BACKGROUND
  A paper-based, multiplexed, microfluidic assay has been developed to visually measure alanine aminotransferase (ALT) in a fingerstick sample, generating rapid, semi-quantitative results. Prior studies indicated a need for improved accuracy; the device was subsequently optimized using an FDA-approved automated platform (Abaxis Piccolo Xpress) as a comparator. Here, we evaluated the performance of the optimized paper test for measurement of ALT in fingerstick blood and serum, as compared to Abaxis and Roche/Hitachi platforms. To evaluate feasibility of remote results interpretation, we also compared reading cell phone camera images of completed tests to reading the device in real time.
  
  
  METHODS
  96 ambulatory patients with varied baseline ALT concentration underwent fingerstick testing using the paper device; cell phone images of completed devices were taken and texted to a blinded off-site reader. Venipuncture serum was obtained from 93/96 participants for routine clinical testing (Roche/Hitachi); subsequently, 88/93 serum samples were captured and applied to paper and Abaxis platforms. Paper test and reference standard results were compared by Bland-Altman analysis.
  
  
  RESULTS
  For serum, there was excellent agreement between paper test and Abaxis results, with negligible bias (+4.5 U/L). Abaxis results were systematically 8.6% lower than Roche/Hitachi results. ALT values in fingerstick samples tested on paper were systematically lower than values in paired serum tested on paper (bias -23.6 U/L) or Abaxis (bias -18.4 U/L); a correction factor was developed for the paper device to match fingerstick blood to serum. Visual reads of cell phone images closely matched reads made in real time (bias +5.5 U/L).
  
  
  CONCLUSIONS
  The paper ALT test is highly accurate for serum testing, matching the reference method against which it was optimized better than the reference methods matched each other. A systematic difference exists between ALT values in fingerstick and paired serum samples, and can be addressed by application of a correction factor to fingerstick values. Remote reading of this device is feasible.
authors.affiliation: Diagnostics For All, Cambridge, Massachusetts, United States of America.
authors.forename: Sidhartha
authors.initials: S
authors.lastname: Jain
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Radha
authors.initials: R
authors.lastname: Rajasingham
authors.affiliation: The Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Boston, Massachusetts, United States of America; Tufts Clinical and Translational Science Institute, Tufts University, Boston, Massachusetts, United States of America.
authors.forename: Farzad
authors.initials: F
authors.lastname: Noubary
authors.affiliation: Diagnostics For All, Cambridge, Massachusetts, United States of America.
authors.forename: Erin
authors.initials: E
authors.lastname: Coonahan
authors.affiliation: Diagnostics For All, Cambridge, Massachusetts, United States of America.
authors.forename: Ryan
authors.initials: R
authors.lastname: Schoeplein
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Rachel
authors.initials: R
authors.lastname: Baden
authors.affiliation: Division of Hepatology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Curry
authors.affiliation: Division of Hepatology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.
authors.forename: Nezam
authors.initials: N
authors.lastname: Afdhal
authors.affiliation: Diagnostics For All, Cambridge, Massachusetts, United States of America.
authors.forename: Shailendra
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America; Department of Laboratory Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America.
authors.forename: Nira R
authors.initials: NR
authors.lastname: Pollock
mesh_terms: D000410:Alanine Transaminase / Q000097:blood*; D001774:Blood Chemical Analysis / Q000295:instrumentation* / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D018962:Phlebotomy; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity
chemical_list: D011933:Reagent Kits, Diagnostic; D000410:Alanine Transaminase