INTERPRETATION INFORMATION SHEET

Transcription

1 Creative Testing Solutions 2424 West Erie Dr Highway Martin Luther King Jr. St. No. Tempe, AZ Bedford, TX St. Petersburg, FL INTERPRETATION INFORMATION SHEET Human Immunodeficiency Virus (HIV) Serology Anti-HIV-1/HIV-2 Plus O EIA: This enzyme-linked immunoassay (EIA) allows simultaneous detection of antibodies to HIV-1 and HIV-2, including HIV-1 Group O. It does not discriminate between HIV-1 and HIV-2 reactivity. An HIV-1, HIV-2 or dual infection can only be confirmed serologically by parallel testing against both antigens using specific EIA and confirmatory assays. Anti-HIV-2 EIA: This enzyme-linked immunoassay (EIA) detects antibodies to HIV-2. However, repeatedly reactive specimens may contain specific antibodies to HIV-2, cross-reacting antibodies to HIV-1, or be non-specifically reactive. Therefore, additional, more specific or supplemental tests for antibodies to both HIV-1 and HIV-2 should be performed. Anti-HIV-1 IFA: See separate sheet. Anti-HIV-1 or Anti-HIV-2 Western Blot: See separate sheet. Final interpretations of any serology assay should also consider the results from the nucleic acid amplification assay and additional medical history. A negative serology test does not exclude the possibility of infection with HIV-1.

2 INTERPRETATION INFORMATION SHEET Human Immunodeficiency Virus Type 1 (HIV-1) Nucleic Acid Testing (NAT) Procleix Ultrio HIV-1/HCV/HBV Assay: This assay utilizes target amplification nucleic acid probe technology for the detection of HIV-1 and HCV RNA and HBV DNA. The screen assay is referred to as Ultrio testing which does not discriminate between HIV-1 and HCV RNA and/or HBV DNA. Specimens found to be reactive upon Ultrio testing are then tested in HIV-1, HCV and HBV Discriminatory Assays (dhiv, dhcv, dhbv assays) to determine if they are reactive for HIV, HCV, and/or HBV. It is possible for all three discriminatory tests to be non-reactive. This may indicate a false positive Ultrio screen test. All assays have a chemiluminescent signal produced by a hybridized probe, which is measured by a luminometer and reported as Relative Light Units (RLU). dhiv-1 Assay: This assay utilizes HIV-1 specific probe reagent directed against specific conserved regions in the viral genome to determine the presence of HIV-1 Virus by Transcription Mediated Amplification (TMA). Roche AmpliScreen HIV-1 Assay: This assay utilizes Polymerase Chain Reaction (PCR) technology for the detection of HIV-1 RNA. This assay detects probe-bound amplified product by colorimetric determination. Final interpretations of any serology assay should also consider the results from the nucleic acid amplification assay and additional medical history.

3 INTERPRETATION OF ANTI-HIV-1 IFA RESULTS The HIV-1 immunofluorescence assay (IFA) is a qualitative test for detection of antibodies to HIV-1 and is intended to be used as an additional, more specific test in specimens found to be repeatedly reactive by screening procedures such as EIA. In this assay, specific HIV-1 antibodies present in a specimen bind to HIV-1 infected human T cells which are fixed to a microscope slide. Uninfected cells are included on the microscope slide for comparison purposes. Bound HIV-1 antibodies are detected with anti-human immunoglobulin conjugated to fluorescein isothiocyanate, which fluoresces when exposed to UV light. Interpretation of the degree and pattern of fluorescence of the infected cells compared to uninfected cells determines the HIV-1 status of a sample. HIV-1 IFA results are interpreted as Positive, Negative or Indeterminate. POSITIVE: A specimen is interpreted as positive when there is a specific cytoplasmic staining pattern in the HIV- 1 infected cells and there is a significant difference in the intensity of fluorescent staining and the pattern of fluorescence between the HIV-1 infected and uninfected cells. Although a positive IFA for antibodies to HIV-1 usually indicates infection with the virus, a diagnosis of Acquired Immunodeficiency Syndrome, AIDS, can only be established on clinical grounds, provided that an individual meets the case definition of AIDS established by the Centers for Disease Control. ACTION REQUIRED: It is imperative an inquiry be made regarding blood donation history and pertinent information forwarded to the Medical Director or Technical Director of the local blood bank, regardless of where the donation may have taken place. The patient must be assured confidentiality will be maintained. NEGATIVE: A specimen is interpreted as negative when there is no specific fluorescent staining of the infected cells and there is no significant difference between the HIV-1 infected and uninfected cells. INDETERMINATE: A specimen is interpreted as indeterminate when there is fluorescent staining present in both the HIV- 1 infected and uninfected cells OR when it is not possible to clearly differentiate the intensity of fluorescent staining and the pattern of fluorescence between the HIV-1 infected and uninfected cells OR when duplicates are discordant. NOTE: A sample with an initial indeterminate result is retested in duplicate before a final interpretation is made. Indeterminate IFA interpretation does not imply that HIV-1 antibodies are, or are not, present in the specimen. It means that the HIV-1 status cannot be resolved and results must not be considered positive or negative. In most cases, indeterminate IFA results are due to the presence of nonspecific staining. Non-specific staining can occur as a result of a variety of conditions and may mask the presence of specific HIV-1 staining. The correct evaluation in such situations must be based on subsequent testing and clinical evaluation. REFERENCES: Sanochemia Pharmazeutika AG Fluorognost TM HIV-1 IFA (product insert) April 2005.

4 INTERPRETATION OF ANTI-HIV-1* OR ANTI-HIV-2** WESTERN BLOT RESULTS Western blot results are interpreted as Positive, Negative or Indeterminate, depending upon the presence or absence of reactivity to the various HIV gene products: GAG proteins: POL proteins: ENV proteins: HIV-1 = p18, p24, p40, p55 HIV-2 = p15, p26 HIV-1 = p31, p51, p65 HIV-2 = p31, p68/58/55 HIV-1 = gp41, gp120, gp160 HIV-2 = gp36, gp36 trimer (gp105), gp120, gp140 POSITIVE - HIV-1: Reactivity to at least two of the major bands: gp120/gp160, gp41 or p24. HIV-2: Reactivity to two env bands or p26 and one env band. Antibody reactivity indicates possible infection and alone is not diagnostic of AIDS. Although a persistently positive immunoblot for antibodies to HIV-1 indicates infection with the virus, a diagnosis of Acquired Immunodeficiency Syndrome or AIDS can only be made on clinical grounds if an individual meets the case definitions of AIDS established by the Centers for Disease Control. Specimens with reactivity for ENV (envelope) proteins only (gp41 and gp120/gp160 for HIV-1 or gp36, gp105, gp120 and gp140 for HIV-2) may meet the criteria for positive even though reactivity to only one gene product is demonstrable. Individuals with this pattern of reactivity who have no risk factors for infection or whose risk history is undetermined must be carefully evaluated using four to six week followup testing and/or additional more sensitive or specific tests such as Nucleic Acid Amplification Testing (NAT) prior to determination of true HIV status. ACTION REQUIRED: It is imperative an inquiry be made regarding blood donation history and pertinent information forwarded to the Medical Director or Technical Director of the local blood bank, regardless of where the donation may have taken place. The patient must be assured confidentiality will be maintained. NEGATIVE - No reactivity is present. INDETERMINATE - Reactivity which does not meet the criteria for positive. Persons who have recently seroconverted may display incomplete patterns but will develop increased reactivity when followed for a period of one to six months. Persons with HIV infection may also have incomplete patterns due to the natural course of the infection or other immunodeficiencies. In addition, individuals infected with HIV-2 may have indeterminate banding patterns using an HIV-1 Western blot. Conversely, persons at low risk for infection may have nonspecific reactions, which may persist but not evolve into more extensive patterns over time. Studies show that non-viral bands are stable and have not been associated with HIV infection. NOTE: Indeterminate results should not be considered either positive OR negative due to variation in test performance and uncertainty associated with indeterminate immunoblots. Additional testing and clinical evaluation must be utilized to correctly evaluate an indeterminate result. *Genetic Systems anti-hiv-1 Western blot **California State Health Department in-house Western blot California State Health Department reports HIV-2 Western blot as inconclusive

5 UNREADABLE When the background is as dark or darker than the control band used to determine a +/- level of reactivity, the laboratory cannot determine or distinguish if there might be viral bands present under the background of reactivity. When this happens, the band location is graded as U to indicate that at that location, the background interferes with the ability to read viral banding. The final interpretation of the blot is unreadable if there are no other bands identified. The blot is interpreted as indeterminate if there are other bands identified that do not meet the criteria of positive. In most cases, a follow-up sample is requested for clarification especially if any of the major viral bands used for the interpretation of a positive blot are unreadable. REFERENCES: Genetic Systems HIV-1Western Blot (Product Insert) October Transfusion 1996: Vol. 36, p37-44 (Frequency of HIV Infection Among Contemporary anti-hiv-1 and anti-hiv 1/2 Supplemental Test Indeterminate Blood Donors by M. Busch, et.al.). Transfusion 1995: Vol. 35, p (Long Term Follow-up of Blood Donors with Indeterminate Human Immunodeficiency Virus Type 1 Results on Western Blot by JB Jackson, et. al.). Morbidity and Mortality Weekly Report - October 11, 1991: Vol 40, No 40, p Morbidity and Mortality Weekly Report - July 21, 1989: Vol 38, No S-7. Journal of the American Medical Association - August 5, 1988: Vol 260, No. 5, p Journal of Clinical Immunology - Fall 1988: Vol 11, No. 3, p HIV-INT (Rev. 12)