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PubMed2004

[SHCS and the laboratory diagnosis of HIV infection--from the development of the HIV Western blot to virus quantification and clinically relevant individual virus characterization].

The first reliable diagnostic tools for the diagnosis of HIV infection, Western blot and ELISA, were created 20 years ago in the U.S., using initially sera from AIDS patients diagnosed clinically in Switzerland. In Swiss laboratories the diagnosis of HIV infection today is established by using 4th generation screening tests which detect both antibodies and p24 antigen while in the doctor's surgery a rapid antibody assay is used. Confirmation in authorized confirmatory labs relies on a set of different minimal combinations of positive test results derived from both the first and second blood specimen. In patients with a confirmed diagnosis of HIV infection, two further principal questions arise concerning, on the one hand, the virus load and, on the other hand, some clinically relevant properties of the infecting virus (type or subtype, resistance against antiretroviral drugs). The paper starts with a personal flashback to the first days of HIV diagnostics and describes the sensible use of tests available today for answering the above-mentioned principal questions. Alternative methods which can be used when standard tests fail or appear unreliable are mentioned also.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

[New methods in the laboratory diagnosis of chronic glomerulonephritis and chronic pyelonephritis].

Two new laboratory diagnostic tests for chronic glomerulonephritis and pyelonephritis have been developed. The first one is based on electrophoretic mobility of urinary lysozyme under certain conditions, such as the use of 12% polyacrylamide gel with pH of 4.3 and acid electrode buffer with pH of 4.0. After electrophoresis was discontinued, lysozyme position was determined by lysis of Micrococcus lysodeikticus, used as test agents and added to the gel as a suspension prior to polymerization. Urinary lysozyme was found to be in the anode area of the gel in 95% of patients with chronic pyelonephritis, and in its cathode area in 92% of patients with chronic glomerulonephritis. There was no lysozyme in the urine of normal subjects. The other laboratory technique, the ethanol test, is based on comparative assessment of the degree of urinary opacification after ethanol is added in conditions of neutral reaction (following the addition of physiologic saline) and marked alkaline reaction (following the addition of sodium hydroxide solution). The ratio of optic density of the alkaline specimen to that of the neutral specimen was above 1 in patients with chronic glomerulonephritis, and below 1 in patients with chronic pyelonephritis and normal subjects. Examination of biochemical mechanisms of the proposed tests has demonstrated that the pattern of proteinuria is the most important factor affecting the results.

Adolescent↗
PubMed1991

Laboratory diagnosis of toxoplasmosis.

Toxoplasmosis is usually diagnosed in the clinical laboratory by detecting antibodies to Toxoplasma gondii, and only rarely by isolating the parasites. A number of serologic tests are used; each has its own advantages and disadvantages. The methods of diagnosis and their interpretations differ for each clinical category of infection.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Laboratory diagnosis of Gardnerella vaginalis vaginosis.

An evaluation of various laboratory detection methods and characteristics of Gardnerella vaginalis was made using high vaginal swab samples of 470 out patient clinic--attending women. Gram stain for 'clue cells' showed positive results in 118 (25.1%)cases; culture, in 100 cases, (213%) and Amine Odour (213%), in 26 cases 5.5%, Majority, 71 cases, of the culture-positive results were associated with a pH value of 6 to 7. Gardnerella vaginalis grew predominantly in enriched culture media: Modified peptone-starch dextrose blood agar used for primary culture of organism, and also proteose peptone broth + cooked meat; Brain-heart infusion broth + 5% human serum; Brain heart infusion starch agar + 5% blood, and chocolate agar. Gardnerella vaginalis culture-positive samples also exhibited positive biochemical reactions with the hydrolysis of starch sensitivity to Bacitracin and 50 microg metronidazole, and haemolysis on human blood agar. Carbohydrate fermentation test was positive for all culture-positive cases, 100% for starch and maltose only, and negative for all the cases, 0% for Mannitol and glycerol.

Bacteriological Techniques↗
PubMed1993

Update on laboratory diagnosis and prognosis of acute pancreatitis.

In this review, the relative values of serum pancreatic enzyme assays and other laboratory tests for diagnosis and prognosis of acute pancreatitis have been evaluated. It is concluded that serum lipase measurement should be the preferred diagnostic method since it is as simple and accurate as amylase assay, all the while being more specific. As for prognosis, among the several biochemical tests now available, the most useful for clinical practice is serum C-reactive protein determination.

Acute Disease↗
PubMed1983

Laboratory diagnosis of cystic fibrosis.

The demonstration of abnormally high concentrations of electrolytes in eccrine sweat is still the only practical laboratory procedure available for diagnosis of cystic fibrosis. Properly performed, the sweat test is very reliable, but there are many published reports that all of the methods in current use frequently generate incorrect diagnoses. Analysis of potential for error in sweat test methods shows that of the three essential phases involved, stimulation, collection, and analysis, the major cause of intrinsic inaccuracy occurs in the collection process. In this case the problem is due to condensate formation, which leads to the subsequent analysis of nonrepresentative sweat. Human error is also an important cause of false results and is a direct function of the number of critical manual operations involved in the technic. This review provides a critical examination of sweat test methods, identifying problem areas and suggesting ways to improve procedures in the interests of clinically reliable laboratory data in support of diagnosis.

Adolescent↗
PubMed2004

Laboratory diagnosis of pertussis infections: the role of PCR and serology.

This study reports on practical laboratory aspects of pertussis diagnosis. PCR assays were applied to respiratory specimens obtained during a large study of infants (less than 5 months old) admitted to paediatric intensive care units (n = 122), children (less than 15 years old) admitted to paediatric wards (n = 16) and their household contacts (n = 320). Estimation of antibodies to pertussis toxin and culture for Bordetella pertussis were attempted on specimens from the same patients, where available, and the overall utility of the diagnostic PCR assays was assessed by comparison to these results. A PCR assay for the human mitochondrial cytochrome oxidase (HMCO) gene was used for quality control of the extracted samples and an internal process control (IPC) was included in each sample to test for PCR inhibition. Four of 458 samples were considered unsuitable (three HMCO negative, one IPC negative) and excluded from further analyses. Positive PCR results were considered valid if they were either (i) positive for both of two B. pertussis gene targets (pertussis toxin S1 promoter and the insertion element IS481), i.e. consensus PCR positive, or (ii) repeatably positive in only one assay. Using these criteria, 52 of 454 (11.5 %) samples were considered as PCR positive for B. pertussis. Six of 356 samples were culture-positive for B. pertussis, 1/88 infants, 3/14 children and 2/254 contacts, giving an overall isolation rate of 1.7 %. Using these data, PCR gave an almost fivefold increase in diagnostic yield compared with culture (McNemar's test; P < 0.0001). Sera from 9/111 infants, 5/10 children and 14/210 contacts were positive. Serology and PCR results showed a high level of agreement (113/121) for infants and children. PCR demonstrated a significant improvement in diagnostic yield over culture. Serological testing also resulted in a significant increase in diagnostic yield compared to culture alone. PCR is a useful technique, but validity of results must be assured by careful control. Rapid diagnosis of B. pertussis infection particularly in infants by PCR, together with serological assays, can enhance surveillance systems for pertussis in all age groups.

Adolescent↗
PubMed2001

Laboratory diagnosis of heparin-induced thrombocytopenia: advantages of a functional flow cytometric test in comparison to the heparin-induced platelet-activation test.

Nearly one third of patients with heparin-induced thrombocytopenia (HIT) will progress to overt thrombosis. Owing to the severity of HIT, a reliable prompt diagnosis is mandatory. In this study 248 consecutive samples from patients referred to our laboratory for HIT diagnosis and 97 specimens from normal controls were prospectively evaluated in parallel using the heparin-induced platelet aggregation (HIPA) test and a flow cytometric (FC) test. The HIPA test resulted in 214 negative, 17 indeterminate and 17 positive samples of patients. The FC method detects activated platelets induced by heparin-immune complexes using the highly sensitive recombinant probe annexin V and pooled platelets from multiple donors. The criteria for positive FC test results included an increase in platelet activiation of at least 11% at 0.3 IU/mL heparin concentration in the tube, and a ratio of more than 1.5 between platelet activation at 0.3 and 200 IU/mL heparin. According to the cut-off level 17 patients who showed indeteminate HIPA test results had 14 negative and 3 indeterminate corresponding FC test results. Only one of these patients (HIPA test indeterminate, FC test indeterminate) had no other obvious medical cause for thrombocytopenia than HIT. Infections or inflammations did not show any association with the FC test results, whereas thromboembolic events displayed a significant patelet activation at pharmacological heparin concentration. Therefore the FC test is associated to the complications of HIT. In conclusion, the FC test, which is fast and practical, showed a good agreement with the HIPA test and may be an accurate and useful test for HIT.

Annexin A5↗
PubMed1988

Laboratory diagnosis of Clostridium difficile-associated diarrhoea.

This paper reviews the various laboratory procedures available for the isolation and identification of Clostridium difficile and the detection of toxins produced by this organism. Laboratories should be selective in determining which patients require investigation for Clostridium difficile-associated diarrhoea. Transport and storage of stool specimens at 4 degrees C is recommended when delays in processing may occur. Tissue culture techniques are still the best method for detection of cytotoxin and a variety of cell lines can be used. Other methods for detecting cytotoxin, and methods for detecting other toxins are not sufficiently developed yet to warrant introduction into diagnostic laboratories. Culture techniques remain the most sensitive for diagnosis, particularly since the development of a variety of enrichment techniques. Cycloserine cefoxitin fructose agar is still adequate, although reduced concentrations of antimicrobial agents are necessary, and improvements, such as the addition of sodium taurocholate, increase the recovery of spores. Enrichment cultures have markedly increased isolation rates for Clostridium difficile but the significance of these isolates needs to be carefully evaluated. Until simpler and more reliable tests are available in clinical laboratories for the detection of toxins, the isolation of Clostridium difficile from patients with diarrhoeal disease should be considered paramount.

Bacterial Toxins↗
PubMed2005

Reduction in turnaround time for laboratory diagnosis of pulmonary tuberculosis by routine use of a nucleic acid amplification test.

Every first diagnostic specimen from suspected patients with pulmonary TB was tested by a nucleic acid amplification test (NAAT) to determine the reduction in turnaround time (TAT) for detecting Mycobacterium tuberculosis (MTB) that was possible under normal laboratory operating conditions. NAAT (Gen-Probe Mycobacterium tuberculosis Direct Testtrade mark) was performed on the first specimen and liquid culture (BACTEC 460), solid culture (Lowenstein-Jensen [LJ] agar and selective 7H11 [7H11S] agar), and fluorescent acid-fast bacilli (AFB) smear were performed on all 3 specimens from each patient. Eighty-one (10.2%) of 797 patients tested were diagnosed with pulmonary TB. The sensitivity of NAAT, BACTEC, LJ, 7H11S, and smear for the first specimen was 90%, 85%, 67%, 53%, and 58%, respectively, whereas the sensitivity for the series of 3 specimens was 90%, 95%, 74%, 74%, and 70%, respectively. Positive predictive value was 100% for all tests except AFB smear, which was 79%. The time to detect 75% of all TB cases was 4 days for NAAT and 21 days for liquid culture; other tests had a sensitivity of less than 75%. Identification and testing every first diagnostic specimen by NAAT has the potential to reduce the overall TAT for laboratory TB diagnosis by approximately 2 weeks.

DNA, Bacterial↗
PubMed1986

Antemortem laboratory diagnosis of Alzheimer's disease.

The accuracy of diagnosis for AD by conventional clinical and laboratory means is in the order of 80%. Neurophysiological techniques (EEG, evoked potentials) show abnormalities in AD that could prove to be useful for diagnosis after pharmacological challenges. CSF analysis show a reduction of the concentration of various neuropeptides, reduction shared by other types of dementias. Among the existing imaging techniques PET using 18F-fluorodeoxyglucose is the most diagnostic in AD because of the early and often asymmetrical decrease in parietotemporal metabolic activity. Cortical biopsy with histological and biochemical analysis can provide an accurate in vivo diagnosis of AD.

Alzheimer Disease↗