Antituberculosis IgG antibodies as a marker of active Mycobacterium tuberculosis disease.

Anti-Mycobacterium tuberculosis IgG antibodies may aid in the diagnosis of active M. tuberculosis disease. We studied whether anti-M. tuberculosis IgG antibodies are elevated in active M. tuberculosis disease and assessed factors contributing to false-positive and -negative results. A retrospective study of 2,150 individuals tested by the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was conducted at the University of Utah, ARUP Laboratories, November 2008 to December 2010. All samples were tested with the InBios Active TbDetect antituberculosis (anti-TB) IgG antibody assay. Of 1,044 patients with a positive QFT-GIT, 59 (5.7%) were positive for M. tuberculosis antibodies. Fourteen of 1,106 (1.3%) with a negative or indeterminate QFT-GIT were positive for M. tuberculosis antibodies. M. tuberculosis antibody tests were positive in 61.5% with confirmed active M. tuberculosis disease and other mycobacterial infections. Over half of the false-negative M. tuberculosis antibody tests occurred in patients ≥ 90 years of age. False positives were seen in 12.9% of autoimmune patients. The odds ratio of being positive by the QFT-GIT and the InBios TB IgG assay increased with confirmed M. tuberculosis disease or highly suspected M. tuberculosis disease and was 86.7 (95% confidence interval [CI], 34.4 to 218.5) in these two groups compared to patients negative by both tests. Although anti-M. tuberculosis antibodies can be detected in patients with active M. tuberculosis disease, caution should be used with patients where immunoglobulin levels may be decreased or patients with autoantibodies.

Epstein-Barr viral load as a marker of lymphoma in AIDS patients.

Epstein-Barr virus (EBV) is implicated in the pathogenesis of acquired immunodeficiency syndrome (AIDS) lymphoma, and viral DNA is present within the malignant cells in about half of affected patients. We examined the extent to which EBV viral load is elevated in the plasma of AIDS lymphoma patients compared to AIDS patients with opportunistic infections. Sixty-one AIDS patients were studied including 35 with lymphoma (24 non-Hodgkin, six Hodgkin, and five brain lymphoma) and 26 with various opportunistic infections. In situ hybridization revealed EBV encoded RNA (EBER) expression in the malignant cells of 17/28 AIDS lymphomas (61%). In 232 serial plasma samples from 35 lymphoma patients and in 128 samples from AIDS controls, EBV viral load was assayed by quantitative-polymerase chain reaction (Q-PCR) using a TaqMan probe targeting the BamH1W sequence. EBV was detected in plasma from all 17 EBER-positive AIDS lymphoma patients, with viral loads ranging from 34 to 1,500,000 copies per ml (median 3,210). Viral load usually fell rapidly upon initiation of lymphoma therapy and remained undetectable except in two patients with persistent tumor. In 11 AIDS patients, whose lymphoma lacked EBER expression, and in 26 control patients without lymphoma, levels of EBV in plasma were usually low or undetectable (range 0-1,995 and 0-2,409, median 0 and 0, respectively). There was no association between EBV viral load and human immunodeficiency virus (HIV) load or CD4 count. In conclusion, EBV viral load shows promise as a tool to assist in diagnosis and management of EBV-related lymphoma patients.

Comparison of nucleic acid amplification tests and culture techniques in the detection of Neisseria gonorrhoeae and Chlamydia trachomatis in victims of suspected child sexual abuse.

STUDY OBJECTIVES: (1) To identify factors predictive for gonorrhea and chlamydia positivity by LCR testing based on history and physical findings encountered during the sexual abuse evaluations. (2) To compare Ligase Chain Reaction (LCR), Polymerase Chain Reaction (PCR), and culture methods in the detection of chlamydia and gonorrhea infection among prepubertal and adolescent girls referred for sexual abuse evaluations. DESIGN: Prevalence odds ratios and logistic regression analysis were used to identify factors among patients' physical symptoms and signs, history of sexual activity, and abuse characteristics that were associated with positive test results for gonorrhea and chlamydia. The Kappa statistic was used to perform pairwise comparisons of LCR, PCR, and culture identification of gonorrhea and chlamydia infection. SETTING: A specialized sexual abuse clinic in San Antonio, Texas. PARTICIPANTS: A consecutive sample of 229 girls between the ages of 6 and 20 who reported, or had indicators of, abusive genital-genital or genital-anal contact. MAIN OUTCOME MEASURES: Patients' history and physical findings predicting positive test results for gonorrhea and chlamydia infection; and relative sensitivity of testing sites (vaginal swab and urine) and methodologies (LCR, PCR, and culture) in identifying gonorrhea and chlamydia infection. RESULTS: (1) Gonorrhea infection: 3.2% of subjects were positive for gonorrhea by LCR at one or more sites; 2.4% had positive gonorrhea cultures. There was excellent agreement between vaginal swab LCR and PCR; agreement between urine samples was limited by the small number of positive tests. The sole factor that predicted gonorrhea positivity was increased number of white blood cells seen on wet mount. (2) Chlamydia infection: 11.1% of subjects were positive for chlamydia by at least one LCR test; only 0.8% had positive chlamydia cultures. Both urine and vaginal swab testing showed good agreement between PCR and LCR but not between culture and either of the newer methodologies. Factors that predicted chlamydia positivity were: patient history of consensual sexual contact, patient history of vaginal discharge, and the presence of concerning or definitive findings of genital trauma. CONCLUSIONS: While LCR, PCR, and culture techniques appeared comparable for detecting gonorrhea, LCR techniques detected significantly more patients with chlamydia infection when compared with the culture technique. PCR was comparable to LCR in detecting chlamydia infection. The LCR vaginal swab detected more patients with chlamydia and gonorrhea than the LCR urine sample. Risk factors for chlamydia and gonorrhea infection were present in most, but not all, of the children with positive LCR findings. LCR and PCR appear to detect more chlamydial and gonorrheal infections than do cultures.

Quantitation of CMV by real-time PCR in transfusable RBC units.

BACKGROUND: CMV is one of the most significant pathogens infecting immunocompromised individuals. CMV is transmissible through transfusion of blood components. The goal of this study was to measure CMV levels in RBC units using a sensitive and quantitative DNA amplification assay. STUDY DESIGN AND METHODS: An assay to measure CMV load was developed by using real-time PCR to target the major immediate early viral gene. A probe (TaqMan, Applied Biosystems) was used to confirm product specificity and to permit quantitation of CMV in blood samples on a sequence detection system (ABI Prism 7700, Applied Biosystems). RESULTS: The assay was shown to be accurate, linear, and sensitive to as few as five copies of CMV DNA per PCR. The assay was applied to aliquots of RBC units from 203 healthy donors, 110 of whom were seropositive for CMV. CMV DNA was not detected in any of the 203 RBC samples. CONCLUSION: The findings statistically imply that at least 98.5 percent of RBC units have a CMV load of less than 250 copies per mL. Future clinical studies on larger numbers of units are required to determine the utility of real-time PCR in evaluating the risk of CMV transmission and in confirming the efficacy of WBC reduction.