[Evaluation of an IgG avidity commercial test: contribution to diagnosis of primary infection caused by Toxoplasma gondii]

INTRODUCTION

Toxoplasmosis (T) is a major chronic parasitic infection in immunocompromised patients and pregnant women. It is important to discriminate between acute phase (AT) and chronic phase (CT). Diagnosis is serological in immunocompetent patients (concentration of IgG and IgM).

OBJECTIVE

To evaluate the utility of an IgG avidity test (A-IgG) to identify the acute and chronic stage. Avidity is the strength of affinity between a specific immunoglobulin and the protein antigenic epitope of the infecting agent, an affinity that increases over time.

PATIENTS AND METHODS

We used a qualitative kit that measures the avidity of IgG, discriminating the two phases. In 35 patients with clinical diagnosis of AT and/or CT, IgG, IgM and IgG A (VIDAS®) were performed.

RESULTS

Patients with AT were positive for IgM and IgG, but presented weak avidity. In the 21 cases with CT, 52% (n: 11) were IgM positive and 100% (n: 21) had positive IgG with strong avidity.

DISCUSSION

The results confirm that the test of A-IgG may be useful in the diagnosis of AT, and has 100% concordance with reference test (qualitative IgM + quantitative IgG). The result is available within 24 hrs, and may be useful in diagnosis of AT in pregnant women.

[Part V. Laboratory diagnosis of Chagas disease]

In this fifth part of Guidelines for Chagas disease, diagnostic techniques for Trypanosoma cruzi infection in humans are reviewed, the interpretation of laboratory results and an algorithm for laboratory diagnosis in immunocompetent hosts are presented. Chagas disease may be diagnosed by three kinds of techniques: direct, which allow detect the presence of the parasite in different kind of samples; indirect, based on the search of immune specific response against T. cruzi antigens and molecular, which detect parasite genetic material. Direct techniques are utilized mainly in acute phase of disease, as the parasite is present in blood of infected host. These techniques do not require be confirmed by other methods. For chronic undetermined phase and for symptomatic phase it is recommended to use indirect techniques; generally, immunoassay techniques (ELISA) that detect IgG antibodies directed against T. cruzi antigens are performed. As false positive results are possible, a positive or undetermined result must be confirmed by at least another technique (indirect immunofluorescence or indirect hemmaglutination). In Chile, confirmation of infection is performed by the Instituto de Salud Pública National Reference Laboratory or at surrogate centers. Molecular methods may be used to make the diagnosis in acute or chronic phase of infection, with more accuracy in the acute phase, and it is mainly recommended to diagnose vertical transmission of T. cruzi as early diagnosis of congenital infection increases the possibility to cure the sibling and besides it is a good marker to evaluate the effectiveness of treatment.

[Part VI. Antiparasitic treatment for Chagas disease]

As expert consensus has been arisen about universal antiparasitic treatment for all patients infected with Trypanosoma cruzi, most important drugs licensed for Chagas disease treatment are reviewed: nifurtimox and benznidazol, their mechanisms of action, doses, treatment schedules, adverse effects and contraindications. Two other drugs used for Chagas disease treatment, for which a Chilean experience may be exhibited, are allopurinol and itraconazole. Indications for treatment of Chagas disease in immunocompetent patients and immunocompromised hosts are detailed. This chapter refers besides to the evaluation and monitoring of antiparasitic therapy in immunocompromised patients, the availability of drugs and includes various forms facsimiles suggested to perform clinical and laboratory follow up of patients that undergo treatment, indicating the prescribed drug, adverse effects and time of follow up.

[Seroepidemiological evidence of human exposure to Anaplasma sp in Santiago, Chile]

OBJECTIVES AND METHODS

To find more evidence of human exposure to Anaplasma sp in Chile, we studied 108 contacts of dogs with canine ehrlichiosis (CE) (risk group) and 61 persons without tick or CE cases contact (control group). A survey including risk factors and history of diseases compatible with ehrlichiosis/ anaplasmosis was applied to the risk group. Serum IgG anti-Anaplasma sp antibodies were determined in both groups.

RESULTS

A significant difference was found in the prevalence of anti-Anaplasma sp antibodies in the risk group compared with the control group (18,5 versus 3,3%), p < 0,005. No risk factors associated to seropositivity were found, nor persons with history suggesting ehrlichiosis/anaplasmosis. Ninety four percent of the houses of the risk group had tick infestation.

DISCUSSION

A greater risk of exposition to Anaplasma sp is documented in people living in close contact with CE cases and in houses with tick infestation.

[Guidelines for chagas disease: Part IV. Chagas disease in immune compromised patients]

A summary of different kind of immune suppressed hosts and the importance of Trypanosoma cruzi infection in this group of patients is presented. Then, most relevant aspects of immune compromised host-parasite interaction are analyzed such as the moment of acquiring the infection, immune compromise level, mechanisms of acquisition the infection and geographic region. Clinical features of primary infection and reactivation of infection in chronic Chagasic patients are described making special emphasis in solid organ transplant and BMT. Chagas disease in AIDS patients is discussed including its treatment, follow up, monitoring the immune compromise level and prophylaxis.

[Guidelines for Chagas disease: Part III. Chagas disease in donors to blood banks]

In this chapter it is emphasized the importance to guarantee safety and high quality blood transfusions. Besides, the following topics are analyzed: the importance of Trypanosoma cruzi infection acquired by blood transfusions, the obligatory screening implemented in Chilean blood banks and serological diagnostic techniques used that for, the seroprevalence observed, the importance to confirm results and methods recommended in this purpose and, to notify the donor once the infection is confirmed. In addition a facsímil of a letter used to notify the positive donor is included as guidelines to make advice after, attaching a pro-forma of clinical-epidemiological registration to refer the donor to medical evaluation and treatment.

[Quality of life of elderly subjects living in basic social dwellings]

BACKGROUND

In Chile, the government is providing basic dwellings to poor elderly subjects that do not have a place to live. These dwellings may be located in buildings or in codominiums.

AIM

To assess the quality of life perception of elderly subjects whose dwellings are located in buildings or in condominiums.

MATERIAL AND METHODS

The brief version of the quality of life questionnaire designed for the elderly by the World Health Organization (WHOQoL-BREF) was applied to elderly subjects of seven poor communities of Metropolitan Santiago, that lived in basic dwellings located in buildings or condominiums. The questionnaire includes questions about physical, psychological, social relations and environment domains.

RESULTS

The questionnaire was answered by 124 elderly subjects aged 60 to 90 years, living in condominiums and 152 subjects aged 62 to 94 years, living in buildings. Satisfaction was of moderate or high level for physical, psychological and social relations domains. Those living in condominiums had a better satisfaction level in this last domain. The level of satisfaction of the environment domain was moderate and better for those living in condominiums. The perception of quality of life deteriorated along with age.

CONCLUSIONS

Elderly subjects living in basic dwellings located in condominiums have a better quality of life perception than those living in buildings.