Home > SPOTCHECK > Newborn Screening > Phenylalanine


Phenylketonuria (PKU) is a hereditary disease that is caused by the lack of a liver enzyme required to digest phenylalanine. Phenylalanine is an amino acid that is most commonly found in protein-containing foods such as meat, cow’s milk, over the counter infant formulas (both regular and soy) and breast milk.

Astoria-Pacific’s SPOTCHECK Phenylalanine test automates the measure of phenylalanine in the newborn blood sample by first diluting and then dialyzing to remove interfering substances. The phenylalanine in the sample then reacts with ninhydrin in the presence of a dipietide to form a fluorescent end product.  The amount of fluorescence is proportional to the phenylalanine concentration in the sample.

Positive Attributes of Instrumentation and Method:

  • Semi-quantitative results
  • No operator attendance is required after loading sample plate
  • Modular system for easy maintenance
  • Large capacity autosampler
  • Same day turnaround of results
  • Totally automatic – no transfer of sample or reagents from one microtiter plate to another.
  • Can be run simultaneously with Total Galactose and GALT assays

Reagent Prep:
The SPOTCHECK Phenylalanine 50 hour Reagent Kit contains all necessary reagents required for analysis and will provide approximately 50 hours of analyzer run time.  The approximate number of actual samples analyzed per kit is conservatively 2500.  All reagents are pre-weighed, color coded, and have a 2 year shelf life (with refrigeration).

Sample Prep:

  1. Punch one 1/8” spot into microtiter filter plate.
  2. Add buffer for sample elution and shake for 30 minutes.
  3. Filter samples into round bottom microtiter plate.
  4. Place the sample plate on the auto-sampler.

Automated Steps:

  1. Sampler delivers calibrants, controls and samples to the cartridges
  2. Online reagent addition
  3. Online incubation
  4. Fluorometric detector measures fluorescent end product which is proportional to the phenylalanine concentration.

Phenylalanine Continuous Flow Brochure