title: Validation of neurokinin a assays in the United States and Europe.
abstract: OBJECTIVE
  International cooperative group trials require specific, sensitive biomarker assays that are validated between continents. Neurokinin A (NKA) has been shown to be a powerful independent predictor of a poor prognosis in well-differentiated midgut neuroendocrine tumors. We hypothesized that NKA concentrations of clinical specimens evaluated in NKA assays in the United States and the United Kingdom would be equivalent, even though assay techniques were significantly different.
  
  
  METHODS
  Frozen clinical specimen aliquots were shipped from the United States to the United Kingdom (n = 67), and from United Kingdom to the United States (n = 50). In addition, spiked plasma standards and medium-spiked standards were exchanged. Samples from the United States were directly assayed in a radioimmunoassay, whereas the UK specimens were extracted, and the reconstituted specimens assayed in the radioimmunoassay. Neurokinin A values from the 2 studies were analyzed by regression analysis.
  
  
  RESULTS
  The NKA values from the US and UK laboratories were essentially identical (United States to United Kingdom, r = 0.88, P < 0.0001; and United Kingdom to United States, r = 0.96, P < 0.0001).
  
  
  CONCLUSIONS
  Validation of biomarker assays across continents will ensure that laboratory observations made by researchers are equivalent and that prediction of clinical outcomes based on these assays is also reliable.
authors.affiliation: Inter Science Institute, Inglewood, CA, USA.
authors.forename: Paris
authors.initials: P
authors.lastname: Mamikunian
authors.forename: Joy E
authors.initials: JE
authors.lastname: Ardill
authors.forename: Thomas M
authors.initials: TM
authors.lastname: O'Dorisio
authors.forename: Siegfried R
authors.initials: SR
authors.lastname: Krutzik
authors.forename: Aaron I
authors.initials: AI
authors.lastname: Vinik
authors.forename: Vay Liang W
authors.initials: VL
authors.lastname: Go
authors.forename: Lee
authors.initials: L
authors.lastname: Armstrong
authors.forename: Gregg
authors.initials: G
authors.lastname: Mamikunian
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Woltering
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D002138:Calibration; D019411:Clinical Laboratory Techniques / Q000592:standards*; D006801:Humans; D053208:Kaplan-Meier Estimate; D018358:Neuroendocrine Tumors / Q000097:blood* / Q000401:mortality; D015288:Neurokinin A / Q000097:blood*; D015588:Observer Variation; D011237:Predictive Value of Tests; D011379:Prognosis; D011863:Radioimmunoassay / Q000592:standards*; D012015:Reference Standards; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000592:standards
chemical_list: D014408:Biomarkers, Tumor; D015288:Neurokinin A