[Evaluation of the analytic performance of blood collection tubes (BD Vacutainer SST) for the screening of anti-HIV, anti-HTLV, anti-HCV, anti-HBc, anti-CMV antibodies, and of HBs, P24 HIV antigens, and of alanine aminotransferase]. / Evaluation des performances analytiques des tubes à prélèvement (BD vacutainer SST) vis-à-vis de la recherche des Ac anti-VIH, anti-HTLV, anti-VHC, anti-HBc, anti-HBs, anti-CMV, des Ag HBs, P24 VIH, et de l'alanine aminotransférase.

The Laboratory of Viral Diseases Immunology (Laboratoire d'Immunologie des Maladies Virales) of the Northern Region Blood Bank (Etablissement Français du Sang Nord de France) performs between 180.000 and 200.000 viral blood qualifications per year. The use of a serum gel separator evacuated tube should contribute to improve the quality of the pre-analytical phase. However, it must not impact negatively the analytical performances. We evaluated such tube within our specific environment and with the various reagents used in routine. The open study compared the BD Vacutainer plain tube (7 mL, non siliconised) with the BD Vacutainer SST tube (6 mL siliconised with serum gel separator) against the anti-HIV, anti-HTLV, anti-HCV, anti-HBc, anti-HBs, anti-CMV antibodies, the HBs, HIV P24 antigen and the alanine aminotransferase. The study objectives were to find potential gel interference; to verify the diagnostic sensitivity, reagents specificity, and reproducibility. The results analysis show: equivalent performances with the anti-HIV Ab (Anti HIV 1/2 recombinant--Biotest et Genscreen HIV 1/2--Sanofi), anti HIV WB Ab (New Lav Blot 1--Sanofi), anti-HBs Ab (Enzygnost anti-HBs micro--Behring), anti-HBc Ab (HBc Elisa Test System--Ortho), anti-CMV Ab (Enzygnost anti-CMV IgG + M--Behring) kits; lower performances with: The Vironostika HIV Uni Form II plus 0--Organon kit with a -3.5% signal decrease around the ratio R = 2.7 for positive anti-HIV Ab. The Elisa test System 3 Ag HBs-Ortho kit with an increase of the mean ratio of the negative Ag HBs samples; better performances with: the Vironostika HIV 1 Antigen--Organon kit with a +10% signal increase around the threshold ratio R = 1 for positive Ag HIV samples. This deserves further study to verify that the specificity is maintained. The HTLV Type 1 et 2 EIA--Ortho kit with +8% signal increase around the ratio R = 2 for positive anti-HTLV Ab samples without change of the specificity. The Ortho HCV 3.0 Elisa Test System and HTLV Type 1 et 2 EIA kits with a clear and significant improvement of the reproducibility of the anti-HCV and anti-HTLV Ab screenings. The results of this evaluation, together with the intrinsic BD SST tube characteristics, lead to the conclusion that its use would contribute to improve the quality. Because of the specificities of each laboratory, a change of tube type, as with any other material or reagent, request a close monitoring of the first results to confirm the absence of negative effects.

[Detection of trypanosomes in blood by the Quantitative Buffy Coat (QBC) technique: experimental evaluation]. / Détection des trypanosomes dans le sang par la technique du Quantitative Buffy Coat (QBC): évaluation expérimentale.

Microhematocrit centrifugation (Woo test) and miniature anion exchange are the most widely used techniques for routine detection of Trypanosoma brucei gambiense in endemic areas. The QBC technique developed for diagnosis of malaria has been successfully used for detection of trypanosoma in blood. The purpose of this laboratory study was to evaluate the end-point sensitivity of the QBC test in comparison with the Woo test. Decreasing concentrations from 15 x 10(5) to 15 trypanosomes/ml of human blood were tested using the two techniques. Sensitivity was calculated in function of reading time at each concentration. Results showed that the sensitivity of the QBC test was 95% down to a concentration of 450 trypanosomes/ml. In comparison 95% sensitivity of the Woo test was observed only down to 7500 trypanosomes/ml and reading time was twofold longer. These findings were reproducible for two hours after sample preparation but deterioration was rapid thereafter. Given its simplicity and sensitivity, QBC test would appear to be a suitable technique for in-field screening programs for human African trypanosomiasis.

Validation of electronic cell counts by quantitative buffy coat analysis (QBC).

A total of 458 eight blood cell counts, accompanied by blood film reviews of the same samples, were performed with an electronic cell counter and with the QBC. In the great majority of cases, the QBC gave fast and accurate control of the flags from the electronic counter, thus avoiding the necessity for manual validation with its associated risks of infection and contaminations. Furthermore, QBC non readability could be related to microcytosis and hypochromia and hence point to possible cases of congenital or acquired haemoglobinopathy.

[Diagnosis of malaria in Africa using the Parasight F test]. / Le diagnostic des accès palustres en Afrique par le test Parasight F.

The purpose of this study which was carried out in the Central African Republic between January and February 1994 was to evaluate the effectiveness of the Parasight F test in diagnosing malaria in the indigenous population. Comparison of test results in a series of 62 malaria suspects who had been residing in the country for more than 10 years and 67 malaria suspects who had been living abroad showed significant differences but the overall value of the test was satisfactory. The test was specific for Plasmodium falciparum. In-field trials showed that the test could be used effectively by paramedics and community health care workers. Basing the decision to perform antimalarial treatment in semi-immune subjects with suspected malarial solely on the results of the Parasight F test would have led to unwarranted non-treatment in 10% of cases. Presumptive treatment of malaria is justified. The Parasight F test allows identification of Plasmodium falciparum and adaptation of therapy if required by the spread of chemoresistance.

ParaSight-F rapid manual diagnostic test of Plasmodium falciparum infection.

The ParaSight(R)-F test is a qualitative diagnostic test of Plasmodium falciparum, which is based on the detection by a monoclonal antibody of a species-specific soluble antigen (histidine-rich protein (HRP-II)) in whole blood and which can be performed without special equipment. A visual reading is given by a polyclonal antibody coupled with dye-loaded liposomes; when positive, a pink line appears. The test has been compared with microscopic examination of thin blood smears and with Quantitative Buffy Coat malaria test (QBC(R) in a single-blind study. A total of 358 patients who had returned to France from malarial areas and consulted their doctor with symptoms or for a routine examination were enrolled in the study; 33 of them were found to have a falciparum malaria infection by the diagnostic test. On the day of consultation, the specificity of the ParaSight(R)-F test was 99% and its sensitivity 94%. The follow-up of infected patients after treatment showed that the test became negative later than the other reference tests. There was no correlation between antigen persistence and the intensity of the ParaSight(R)-F signal or circulating parasitaemia. No cross-reaction was noted for seven malaria cases due to other Plasmodium species. The test was performed quickly (10 tests in 20 minutes), was easy to read, and required minimal space. For cases of imported malaria, the test's specificity and low threshold for detection could make it a valuable adjunct test. However, in its present form, it cannot replace microscopic techniques which are species-specific and quantitative. In endemic areas, the test seems to be very promising by its results and ease of use according to published field studies.

Rapid in vivo detection of chloroquine resistance by the Quantitative Buffy Coat Malaria Diagnosis System.

The use of the Giemsa-stained thick blood smear for the diagnosis of malaria has not been supplanted since the discovery of the parasite by A. Laveran in 1880. Recently, a new direct diagnosis technique, the Quantitative Buffy Coat (QBC)* Malaria Diagnosis System, has been developed. We compared this technique with the thick blood smear diagnosis in a study of the efficacy of chloroquine therapy in Zaire. A total of 815 subjects were screened; 71 participated in the trial. They were given chloroquine at a dose of 25 mg/kg of body weight over three days and were examined for parasitemia two and seven days after treatment. Chloroquine resistance was detected in 38% of the subjects by thick blood smear and in 45% by the QBC test. Of greater interest was the time required for each diagnosis: an average of 17 min was required to examine microscopic fields with 1,000 leukocytes by thick blood smear analysis compared with less than one min by the QBC system. In addition, we did not observe diminished attention from fatigue by microscopists using the QBC system despite the large number of tests conducted. We conclude that the QBC system is an important tool for studies of drug resistance.