Single donator specimens as advantage in external quality control assessments of infectious diseases MD, PhD Maija Lappalainen and MD Jukka Suni HUSLAB, Department of Virology Labquality Days 10.2.2007
Definitions Quality control refers to the measures that must be included during each assay run to verify that the test is working properly. Quality assurance is defined as the overall program that ensures that the final results reported by the laboratory are correct. Therefore, quality assurance is concerned with much more: that the right test is carried out on the right specimen, and that the right result and right interpretation is delivered to the right person at the right time
Definitions Quality assessment (also known as proficiency testing) is a means to determine the quality of the results generated by the laboratory. Quality assessment is a challenge to the effectiveness of the QA and QC programs. Quality Assessment may be external or internal, examples of external programs include Labquality, NEQAS, and QCMD.
Requirements for EQA what do the standards tell us? SFSEN ISO/IEC 17025:2005 General requirements for the competence of testing and calibration laboratories: 5.9.1 The laboratory shall have quality control procedures for monitoring the validity of tests and calibrations undertaken. The resulting data shall be recorded in such a way that trends are detectable and, where practicable, statistical techniques shall be applied to the reviewing of the results.
Requirements for EQA what do the standards tell us? SFSEN ISO 15189 Medical laboratories. Particular requirements for quality and competence: 5.6.4. External quality assessment programmes should, as far as possible, provide clinically relevant challenges that mimic patient samples and have the effect of checking the entire examination process, including pre and postexamination procedures.
Variables that affect the quality of results The educational background and training of the laboratory personnel The condition of the specimens The controls used in the test runs Reagents Equipment The interpretation of the results The reporting of results
Results and reporting in the diagnosis of infectious diseases Test result interpretation (background, other tests, patient history) Result reported for the clinician
Puzzle a problem designed to test knowledge or patience (The Oxford Handy Dictionary, modified)
External Quality assessment programs; specimens EQA specimens for infectious diseases (serology) are either: (1) Single donator plasma/serum samples or (2) Pooled plasma/serum samples The benefits of using a single donator specimens are: (1) Mimic patient samples (2) Not only samples, but samples with a history (3) A relevant test result combination (4) Less problems with unspecific test results
Serodiagnosis of Hepatitis B virus infection HBsAg : acute or chronic HBV infection HBcAb ja HBsAb: previous HBV infection HBsAb: vaccinated
Example 1. Hepatitis B HBsAg: HBcAb: HBeAg: HBeAb: HBcAbM: HBsAb: HBsAg: HBcAb: HBeAg:!!! HBeAb: HBcAbM: HBsAb:
Epstein Barr Virus, EBV and infectious mononucleosis, IM
EBV associated diseases 95% of people are seropositive Asymptomatic/minor symptoms Often small children Infectious mononucleosis (IM) Children, adolescents Symptomatic disease Adults (hepatitis, jaundice) EBV associated diseases Burkitt lymphoma Nasopharyngeal carcinoma Posttransplant lymphoproliferative disease (PTLD)
Antibody responses in EBVinfection Incubation (12 mos) symptoms (12 wks) recovery 6 mos EBNA and Avidity VCA IgG VCA IgM Heterophile abs.
EBVinfection Interpretation of serological findings Rapid Ly VCA VCA EBNA1 Interpretation test atypical IgG IgM IgG / / Acute infection Recovered No infection / / Indeterminate Indeterminate Indeterminate Not possible / Not possible
EBVserology Pretest
HIV infection and serology
Diagnostic tests of HIVinfection Detection of antibodies in IgGclass Detection of total antibodies Detection of total antibodies and HIV p24 antigen in the same assay, COMBI Immunoblot (Western blot) of IgGclass of antibodies HIV p24antigen assay HIV1 RNA PCR, qualitative HIV1 RNA PCR, quantitative
HIVserology report targets HIVantibody negative HIVantibody positive Old infection Recent infection Early HAART therapy
A simple scheme for HIV serology algorithm HIVAgAb Combi QUALITATIVE Positive Negative HIVAb HIV p24antigen Report Negative QUANTITATIVE Positive Immunoblot Report with HIV p24antigen
HIV immunoblot (INNOLIA ) 1:1 1:10 1:50 POS NEG AxSYM AxSYM AxSYM AxSYM AxSYM 19.51 8.64 12.05 1.75 0.80