Abstract
BackgroundA 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.Methods96 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.FindingsFor 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).ConclusionsThe 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.
Highlights
Point-of-care (POC) diagnostics are desirable for diagnosis and medical management in resource-constrained settings
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
These diseases disproportionately affect those in resource-limited settings, and with limited or no access to transaminase testing in many of these settings, patients are put at increased risk of complications of drug-induced liver injury (DILI)
Summary
Point-of-care (POC) diagnostics are desirable for diagnosis and medical management in resource-constrained settings. If centralized testing is available, lengthy results turn-around time can lead to patients becoming lost to follow-up, adversely impacting outcomes With these barriers in mind, there has been a recent explosion in the development of POC diagnostics for many applications [1,2,3]. Transaminase monitoring requires equipment for a venous blood draw, a trained phlebotomist, centrifugation to separate serum or plasma, and testing on a large automated platform Such platforms are expensive and require highly trained technicians for testing and maintenance, making them impractical for use and scale-up in many developing countries. Because of these obstacles, in many resource-limited settings, patients on potentially hepatotoxic medications receive minimal or no monitoring during treatment. To evaluate feasibility of remote results interpretation, we compared reading cell phone camera images of completed tests to reading the device in real time
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