Comparison between screening and confirmatory serological assays in blood donors in a Region of South Italy

Linda Sommese, Carmela Iannone, Francesco Cacciatore, Gustavo De Iorio, Claudio Napoli

Research output: Contribution to journalArticlepeer-review


Background: Screening assays are needed in order to guarantee safety of donated blood, but a significant number of safe donations are removed from blood supply because of reactive screening results. It is important to evaluate the positive predictive value (PPV) of screening assays in order to modulate confirmatory algorithm and implement an adequate counseling. Methods: An analysis of 17,912 blood donations has been conducted at Transfusion Medicine at Second University Naples, Italy, in 2009-2012. Serological screening for syphilis, hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) was performed by ARCHITECT (Abbott Diagnostics, Wiesbaden, Germany); repeatedly reactive (RR) samples were checked by respective confirmatory tests. The relationship between sample/cutoff and confirmed seropositivity were analyzed. Results: RR rates were low as expected in blood donors: 0.47% for syphilis, 0.42% for HBV, 0.50% for HCV, and 0.15% for HIV. The specificity on RR + gray zone (GZ) was 99.67%, 99.79%, 99.77%, and 99.88%, respectively; due to the low prevalence, PPV value was 30.6% for syphilis, 50.7% for HBV, 42.2% for HCV, and 18.5% for HIV. These values increased substantially reaching a plateau of 89.3% for syphilis, 94.6% for HBV, 85.7% for HCV, and 100% for HIV at the threshold established by receiver operating characteristics curve analysis. Conclusions: Supplemental testing on samples with high signal by screening assays seems to add little information. GZ settings and confirmatory testing for positive screening results should be designed taking in account several factors, including difference in the natural history among blood-borne infections, the characteristics of first- and second-level tests, and, when available, the results of nucleic acid amplification testing.

Original languageEnglish
Pages (from-to)198-203
Number of pages6
JournalJournal of Clinical Laboratory Analysis
Issue number3
Publication statusPublished - 2014


  • Blood screening
  • CMIA
  • Confirmatory assays
  • NAT
  • Transfusion-transmitted infections

ASJC Scopus subject areas

  • Biochemistry, medical
  • Public Health, Environmental and Occupational Health
  • Hematology
  • Immunology and Allergy
  • Microbiology (medical)
  • Medical Laboratory Technology
  • Clinical Biochemistry
  • Medicine(all)


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