Determination of N-acetylation phenotype using caffeine as a metabolic probe and high-performance liquid chromatography with either ultraviolet detection or electrospray mass spectrometry.

A rapid, sensitive method using liquid chromatography-electrospray mass spectrometry (LC-ES-MS) was developed and evaluated for the simultaneous quantitative determination of caffeine metabolites 1U, 1X and AAMU in human urine. This method involved a simple dilution of urine samples. The chromatographic separation was achieved on a C18 reversed-phase column using a gradient of acetonitrile in 2 mM, pH 3.0 ammonium formate as mobile phase. After ionisation in an electrospray source, mass spectrometric detection was performed in the negative ion, selected ion monitoring mode. This method yielded acceptable accuracy and precision within the range 0.25-50 microg/ml. This analytical method was applied to investigate the N-acetylator phenotype of HIV-infected patients and compared with high-performance liquid chromatography with UV detection. Its specificity was better, which appeared to be absolutely necessary to prevent errors in metabolic ratios and phenotype interpretation.

Prospective study of toxoplasma reactivation by polymerase chain reaction in allogeneic stem-cell transplant recipients.

Toxoplasmosis is a rare but life-threatening complication of allogeneic stem-cell transplantation. Polymerase chain reaction (PCR) offers the possibility to make the diagnosis earlier than conventional techniques, and is then expected to improve the prognosis. We undertook a prospective screening using a competitive PCR in blood in 32 stem-cell transplant recipients. The sampling covered the first 150 days post-transplant, at days 21, 30, 45, 60, 90, 120, and 150. Twenty-four patients had anti-toxoplasma antibodies before transplant. Three of them (12.5%) had transient PCR-positive samples at 21, 45, and 90 days post-transplant, respectively. The three PCR-positive patients were febrile but had no funduscopic examination or cerebral computerised tomography (CT) scan abnormalities. The PCR signal disappeared when the patients were given trimethoprim-sulfamethoxazole, and no full-blown toxoplasmosis was observed. Toxoplasma reactivation evidenced using PCR is frequent in seropositive patients not receiving trimethoprim-sulfamethoxazole during the 1-3 months post-transplant. Toxoplasma PCR should be included in the diagnostic strategy of fever of unexplained origin in allogeneic stem-cell transplant recipients. Then, prompt specific therapy can be initiated to avoid development of full-blown toxoplasmosis.