How likely is environmental or patient cross-contamination of Chlamydia trachomatis DNA to lead to false positive results in patients attending our clinic?

OBJECTIVES: Environmental contamination with DNA from Chlamydia trachomatis (CT) has previously been found in Genitourinary Medicine (GUM) clinics. There are no known cases of cross-contamination of clinical samples and no known nosocomial infections. We investigated whether diagnostic samples could become contaminated from the environment by running dummy sample and carrying out a patient-throughput analysis. A total of 29 748 patients attended clinics over a year. Of these, 2860 (9.6%) had a positive Chlamydia test result. METHOD: (1) A run of dummy samples (60 urine samples and 10 swabs) were processed as normal clinic specimens. (2) Patient-throughput analysis: Patient numbers attending the GUM clinic on a given day was categorised as low, moderate or high. χ(2) Tests were used to look for associations between categorical variables and Chlamydia test positivity. A Poisson regression model was fitted to look at the effect of the number of people in the clinic on the number of positive results in a given day. As some clinics were only run on certain days of the week, a sensitivity analysis was later performed with attendances at non-daily clinics removed. RESULTS: All dummy samples tested negative and we did not find evidence of an association between daily Chlamydia positivity and clinic attendance. CONCLUSIONS: It is unlikely that environmental or cross-contamination of CT has lead to significant numbers of false positive results. Laboratories check for possible cross-contamination routinely. The extension of this simple routine practice to all clinical areas could provide quality assurance, improving confidence in the results in clinics.

Tenofovir-linked hyperparathyroidism is independently associated with the presence of vitamin D deficiency.

BACKGROUND: To determine patient and treatment characteristics associated with vitamin D deficiency (VDD) in an UK inner city HIV-1-positive adult cohort. METHODS: Two hundred twenty-seven HIV-positive patients attending prospectively for routine blood tests in winter had serum 25-hydroxyvitamin D and parathyroid hormone (PTH) concentrations and other routine chemistry measured. Those with and without VDD were defined as having serum 25-hydroxyvitamin D concentrations <50 nmol/L and >75 nmol/L, respectively. Characteristics were compared between patients with and without VDD. The effects of VDD, tenofovir use, and their interaction on chemical measures were investigated. RESULTS: VDD was found in 57% (131 of 227) of patients. Independent associations included nonwhite ethnicity [adjusted odds ratio (95% confidence interval): 7.40 (2.52 to 21.7)], higher random blood glucose [2.38 (1.24 to 4.57) per mmol/L], higher estimated glomerular filtration rate [eGFR: 1.04 (1.01 to 1.06)], and higher PTH [1.19 (1.00 to 1.42)]. PTH was higher in those receiving tenofovir (median 7.2 pmol/L) than other patients (4.3; P < 0.001) overall, but high PTH with tenofovir occurred only in the context of VDD. Tenofovir use was not associated with serum creatinine or eGFR overall but interacted with vitamin D status (P = 0.05 and P = 0.08, respectively), being linked to somewhat higher creatinine and lower eGFR among patients without VDD but higher eGFR in VDD patients. CONCLUSIONS: 25(OH) VDD is associated with tenofovir-linked hyperparathyroidism and also with higher eGFR.

Experience with efavirenz in end-stage renal disease.

There are few data on the use of highly active antiretroviral therapy in HIV-positive patients with end-stage renal disease. We describe the tolerability, safety and efficacy of an efavirenz-containing regimen in one such patient on continuous ambulatory peritoneal dialysis.