Mumps antibody levels among students before a mumps outbreak: in search of a correlate of immunity.

BACKGROUND: In 2006, a mumps outbreak occurred on a university campus despite ≥ 95% coverage of students with 2 doses of measles-mumps-rubella (MMR) vaccine. Using plasma samples from a blood drive held on campus before identification of mumps cases, we compared vaccine-induced preoutbreak mumps antibody levels between individuals who developed mumps (case patients) and those who did not develop mumps (nonpatients). METHODS: Preoutbreak samples were available from 11 case patients, 22 nonpatients who reported mumps exposure but no mumps symptoms, and 103 nonpatients who reported no known exposure and no symptoms. Antibody titers were measured by plaque reduction neutralization assay using Jeryl Lynn vaccine virus and the outbreak virus Iowa-G/USA-06 and by enzyme immunoassay (EIA). RESULTS: Preoutbreak Jeryl Lynn virus neutralization titers were significantly lower among case patients than unexposed nonpatients (P = .023), and EIA results were significantly lower among case patients than exposed nonpatients (P = .007) and unexposed nonpatients (P = .009). Proportionately more case patients than exposed nonpatients had a preoutbreak anti-Jeryl Lynn titer < 31 (64% vs 27%, respectively; P = .065), an anti-Iowa-G/USA-06 titer < 8 (55% vs 14%; P = .033), and EIA index standard ratio < 1.40 (64% vs 9%; P = .002) and < 1.71 (73% vs 14%, P = .001). DISCUSSION: Case patients generally had lower preoutbreak mumps antibody levels than nonpatients. However, titers overlapped and no cutoff points separated all mumps case patients from all nonpatients.

Human T-lymphotropic virus antibody screening of blood donors: rates of false-positive results and evaluation of a potential donor reentry algorithm.

BACKGROUND: Blood donor screening with enzyme immunoassays (EIAs) for antibodies to human T-lymphotropic virus (HTLV)-I, and later to HTLV-I/II, has led to the unnecessary deferral of tens of thousands of individuals. The licensure of the Abbott PRISM HTLV-I/HTLV-II chemiluminescent immunoassay (ChLIA) may permit the reinstatement of historically deferred donors. STUDY DESIGN AND METHODS: The efficacy of a reentry algorithm involving a follow-up sample from EIA-deferred donors testing HTLV-I/II ChLIA nonreactive was evaluated using 386 serologic confirmed-positive samples archived since the inception of anti-HTLV donor screening. Reactivity of the 386 samples by the ChLIA, when coupled with the package insert sensitivity data, may be used to demonstrate efficacy of the reentry algorithm. Donor incidence was also examined from 2008 through 2009 to evaluate changes to the existing HTLV screening policy. RESULTS: From January 1, 1995, to April 28, 2008, a total of 64,052 donors to the American Red Cross were deferred solely because of HTLV EIA false positivity, representing more than 130,000 US donors. HTLV ChLIA identified 386 confirmed-positive donations from 386 randomly selected donors representing reactivity to both the bioMérieux and the Abbott HTLV-I/II EIAs (95% confidence interval [CI], 99.2%-100%); both EIAs have since been discontinued. This is comparable to the detection of 843 of 843 confirmed-positive samples during the ChLIA clinical trials (95% CI, 99.48%-100%). Incident HTLV infections occurred primarily among female repeat donors during 2008 throughout 2009. CONCLUSIONS: Donors testing falsely positive by historic EIAs since 1988 should be considered for reinstatement if a contemporary sample tests ChLIA nonreactive. Changes to the existing screening algorithm seem unlikely since new HTLV infections were detected among repeat donors.

The risk for Chagas' disease in the Midwestern United States organ donor population is low.

PURPOSE: Several recent publications have increased awareness that transplanted organs can transmit infectious diseases. In light of the recent report describing the transmission of Trypanosoma cruzi infection by an organ donor in the United States (MMWR 2002: 51: 210), we have tested archived serum samples from our Organ Procurement Organization's (OPO's) deceased organ donors and live donors from 23 October 1995 through 1 March 2002. METHODS: A total of 1117 serum samples from 558 locally recovered deceased donors, 178 imported deceased donors, and 212 live donors were tested (several duplicates were included). Samples were screened for antibodies to T. cruzi, the protozoan parasite that causes Chagas' disease, with a passive particle agglutination assay (Fujirebio, Inc., Tokyo, Japan). Indeterminate samples (those agglutinating both sensitized and control particles) were absorbed with control antigen and re-tested. Inconclusive samples (those not yielding clearly negative or positive results) were re-tested using the original test format, and if persistently inconclusive, were assayed by radio-immune precipitation (RIPA). RESULTS: Of the 770 local OPO donors (deceased and live donor) and the 178 imported donors tested, 52 (5.5%) were indeterminate, but following absorption, all were negative. Forty-four samples (4.6%) were inconclusive and after re-testing 34 were negative while 10 remained inconclusive. Those 10 samples were found to be negative by RIPA. CONCLUSIONS: The risk of transmission of Chagas' disease by organ transplantation in the Midwestern United States is low because during a 6.5 year period, none of our deceased or live donors tested positive for antibodies to T. cruzi. Although the passive particle agglutination test is simple to perform, easy to interpret and rapid enough to be used in screening organ donors, because of the rate of false positive results, it should only be utilized when the donor population is at high risk for previous exposure to T. cruzi.

Comparative yield of HCV RNA testing in blood donors screened by 2.0 versus 3.0 antibody assays.

BACKGROUND: Two HCV antibody tests (EIA 2.0 [EIA2], Abbott; and the Version 3.0 ELISA [EIA3], Ortho) are currently licensed for screening of US blood donors. Testing of donors for HCV RNA allows comparison of the sensitivities of the two antibody-screening assays. STUDY DESIGN AND METHODS: All allogeneic blood donations at 13 US test sites were screened for HCV RNA by testing plasma minipools using an investigational assay (COBAS AmpliScreen HCV test, v2.0, Roche Molecular Systems). Some sites screened for HCV antibody by EIA2 and some used EIA3. The frequency of RNA-positive and antibody-negative (RNA-pos and Ab-neg) donations among donors screened by each antibody assay was compared. Antibody appearance was assessed in a donor follow-up study. RESULTS: A total of 5.51 x 10(6) donations were screened for HCV RNA. Of these, 2.27 million were screened for antibody by EIA2, and 3.24 million by EIA3. Twenty-three donations were HCV RNA-pos and Ab-neg. The frequency of RNA-pos and Ab-neg donations was higher among donations screened by EIA2 (1 in 134,000), compared to those screened by EIA3 (1 in 540,000) (p = 0.001). Of the 17 RNA-pos and Ab-neg donations identified by test sites that used EIA2, 14 were retested by EIA3 and 10 (71%) were reactive. Most RNA-pos and Ab-neg donors appear to be in the process of seroconversion. Donors that were initially EIA2-negative and EIA3-reactive showed a more prolonged pattern of seroconversion compared to those that were initially nonreactive by both antibody assays. Four donors were EIA2-negative, EIA3-reactive, and RIBA-indeterminate (c33c) for at least 90 days, 1 for more than 317 days. CONCLUSION: EIA3 would have detected the majority of RNA-positive donations missed by EIA2. Some RNA-positive donors are EIA2-negative and EIA3-reactive for a prolonged period of time.