Detection of incipient left ventricular hypertrophy in mild to moderate arterial hypertension with normal electrocardiogram and echocardiogram: a new use for signal-averaged electrocardiography

OBJECTIVE: To assess signal-averaged electrocardiogram (SAECG) for diagnosing incipient left ventricular hypertrophy (LVH). METHODS: A study with 115 individuals was carried out. The individuals were divided as follows: GI - 38 healthy individuals; GII - 47 individuals with mild to moderate hypertension and normal findings on echocardiogram and ECG; and GIII - 30 individuals with hypertension and documented LVH. The magnitude vector of the SAECG was analyzed with the high-pass cutoff frequency of 40 Hz through the bidirectional four-pole Butterworth high-pass digital filter. The mean quadratic root of the total QRS voltage (RMST) and the two-dimensional integral of the QRS area of the spectro-temporal map were analyzed between 0 and 30 Hz for the frequency domain (Int FD), and between 40 and 250 Hz for the time domain (Int TD). The electrocardiographic criterion for LVH was based on the Cornell Product. Left ventricular mass was calculated with the Devereux formula. RESULTS: All parameters analyzed increased from GI to GIII, except for Int FD (GII vs GIII) and RMST log (GII vs GIII). Int TD showed greater accuracy for detecting LVH with an appropriate cutoff > 8 (sensitivity of 55%, specificity of 81%). Positive values (> 8) were found in 56.5% of the G II patients and in 18.4% of the GI patients (p< 0.0005). CONCLUSION: SAECG can be used in the early diagnosis of LVH in hypertensive patients with normal ECG and echocardiogram.

Comparative ELISA reagents for detection of hepatitis B surface antigen (HBsAg)

Conjugates of goat anti-HBs IgG and horseradish peroxidase (HRP) prepared by two different methods, one using NaIO4 and the other SPDP, were compared. Anti-HBs antibodies obtained from goat, rabbit and guinea-pig were tested as capture serum. The ELISA showed a sensitivity similar to RIA and a level of antigen captation ranging from 4.37 to 8.75 nanograms/ml was obtained when rabbit or guinea-pig captures were used combined with both NaIO4 or SPDP conjugates.

Rapid detection by transmission electron microscopy of mycoplasma contamination in sera and cell cultures

Transmission electon microscopy has been employed for the rapid detection of mycoplasma in sera and cell cultures. High speed centrifugation of sera or low speed centrifugation of cell debris, followed by negative staining of the resuspended pellet, detected mycoplasma contamination more frequently than a culture method followed by direct fluorescence (DAPI), which was used as a control procedure. The appearance of the mycoplasma cell border and content gives some information about particle viability.

Detection of viral infection by immunofluorescence in formalin-fixed tissues, pretreated with trypsin

The presence of viral antigen in sections from formalin-fixed and paraffin-embedded human tissues was demonstrated by trypsin digestion followed by direct or indirect immunofluorescence. The specimens may be used for retrospective diagnosis. The immunofluorescence technique has to be adapted to the suspected virus infection on the basis of previous histopathology study. Variations of trypsin concentration time and temperature of incubation, expose different viral antigens and have to be previously tested for each unknown system. For measles virus detection in lung a stronger digestion has to be applied as compared to adenovirus or respiratory disease viruses in the same tisue. Flavivirus in liver tissue needs a weaker digestion. The reproducibility of the method makes it useful as a routine technique in diagnosis of virus infection.

Study of two different enzyme immunoassays for the detection of Mayaro virus antibodies

This paper presents the evaluation of an enzyme immunoassay in which Mayaro virus-infected cultured cells ara used as antigen (EIA-ICC) and an IgM antibody capture ELISA (MAC-ELISA) for Mayaro serologic diagnosis using 114 human sera obtained during a Mayaro outbreak occurred in Bolivia, in 1987. Results were compared with those obtained by haemagglutination-inhibition test (HAI). MAC-ELISA was the most sensitive technique for anti-Mayaro IgM detection. MAC-ELISA was twice sensitive as IgM EIA-ICC. The data shows that MAC-ELISA is a practical and valid technique for diagnosis of recent mayaro infection. IgG-ICC showed hight sensitivity and high specificity compared to HAI. The combination of anti-Mayaro IgG and IgM EIA-ICC results presented the highest sensitivity of the study. Anti-Mayaro IgG and IgM simultaneous detection by ELISA-ICC can be used for recent infection diagnosis (in spite of a less sensitive IgM detection than by MAC-ELISA), for surveillance and sero-epidemiologic studies, and for studies of IgG and IgM responses to Mayaro infection.

Technique for the detection of Toxoplasma gondii antigens in mouse urine

A simple and rapid staphylococcal coagglutination test for the detection of Toxoplasma gondii antigens in mice urine is described. A suspension of protein-A containing Staphylococcus aureus coated with rabbit hyperimmune serum was used as reagent. The sensitivity of the antigen assay was found to be at least 118 ng of the antigen protein per ml. No coagglutination was observed when the reagent was challenged against antigenic solutions of other parasites. The suitability of the method for detecting antigens of T. gondii in urine samples was studied by experimental toxoplasma infection in mice. Before the staphylococcal test, the urine samples were double serially diluted in 0.1 M PBS. From the second day on all samples from infected mice were positive at 1/16 dilution. At this dilution, all samples from non infected mice were negative or did not produce coagglutination. This method might be used in the rapid etiological diagnosis also in human cases of acute toxoplasmosis.

Methods for field detection of resistance to temephos in simuliids. Larval esterase level and topical application of the insecticide to adults

Two practical field methods for indirect detection of simuliid populations resistant to temephos are proposed. The first is based on high esterase activity in resistant larvae and involves adaptations of a filter paper test in which faintly stained spots indicate susceptible populations and strongly stained ones reveal populations resistant to temephos. The second is based on the resistance to the larvicide when adults are topically exposed, and involves the use of diagnostic doses obtained by the comparison between the LD50 for susceptible and resistant populations. The relevance of such methods is discussed in order to help resistance detection in Simulium pertinax Kollar control programmes.

Use of an indirect haemagglutination test, for the detection of Clostridium perfringens type A enterotoxin

An indirect haemagglutination (IH) test is described for the detection of Clostridium perfringens type A enterotoxin, produced by strains isolated from human cases of food poisoning and from contaminated food. Though no strict relationship could be observed between titers in the IH test and the time it took mice to die from the intravenous inoculation of mice (IIM), results of the supernatants examined by both methods demonstrated that the IH test was more sensitive than the ILM one. No unspecific reaction was obtanined int he IH wirh a negative control and the inhibitions of the IH and IIM tests by specific antiserum against C. perfringens enterotoxin showed that the IH test is very spcific. The IH assay is recommended for its sensitivity and easy performance by less-equipped laboratories, by these and other data.