ABSTRACT
SETTING: Tuberculosis Laboratory Network, Argentina. OBJECTIVES: 1) To evaluate the technical quality of smear microscopy for acid-fast bacilli (AFB) supervised in 1983-2001, and 2) to analyse the effect of procedural errors on the results. DESIGN: Registers of technical evaluation results for AFB microscopy were analysed. The quality of specimens, smears, staining and readings were evaluated, as was the relationship between these parameters. RESULTS: The proportion of good quality specimens was considered acceptable. A direct relationship was demonstrated between positivity in results and mucopurulent sputum. The proportion of thin smears was relatively high. Positivity and bacillary count were lower in thin smears. Staining quality was considered good. The average agreement in readings throughout the country was 98%. Nevertheless, the false-positive rate was considered significant, and 46% of false-positive results were associated with defective staining. CONCLUSIONS: The technical quality and agreement in the laboratory network were satisfactory. Nevertheless, improvements need to be made in the following: the quality of the smears, staining and reading, coverage, decentralisation of supervision, the slide selection method and data registration. Operational research on the storage and preservation of slides is also necessary.
Subject(s)
Bacteriological Techniques/standards , Mycobacterium tuberculosis/isolation & purification , Brazil , False Positive Reactions , Humans , Microscopy/standards , Quality Assurance, Health Care , Sensitivity and Specificity , Sputum/microbiology , Tuberculosis, Pulmonary/microbiologyABSTRACT
Confirming the diagnosis of pediatric tuberculosis is cumbersome, due to the clinical features (generally paucibacillary forms) of the disease. This national study was undertaken in order to establish: the features of childhood tuberculosis at the time of diagnosis, the criteria on which the pediatricians based the diagnosis, the bacteriologic contribution to the diagnosis and the quality of notifications to the National Programme. Medical and laboratory records were reviewed for children under 15 years of age who were diagnosed with tuberculosis disease or primary infection during 1995. The study included children cared for at health centres from Argentinean provinces (capital city excluded) where pediatricians accepted to participate. Four hundred cases (17% of childhood notifications to the National Programme) and 81 primary infections were studied. The percentage of children studied by means of chest radiology, presence of symptoms, Mantoux test, case contact investigation and bacteriology were 95.3%, 79.6%, 90.1%, 92.7% and 35% for pulmonary cases, respectively, and 87.7%, 100%, 87.7%, 85.9% and 78.9% for extra-pulmonary cases, respectively. Of the evaluated pulmonary cases, 99.1% had abnormal x-rays, 79.0% had a tuberculin test > or = 10 mm, 79.8% had symptoms and 80.2% had a history of close contact. All extra-pulmonary patients had symptoms at the time of diagnosis; 63.0% had abnormal chest radiograph at diagnosis. Bacteriologic confirmation was achieved in 10.7% of the cases (20.8% and 40.0% of the investigated pulmonary and extra-pulmonary cases, respectively). This study would indicate that the diagnosis is made at relatively early stages of the disease. In general, recommendations of the Argentine Society of Pediatrics were followed. A low rate of bacteriological proof of diagnosis was observed, probably due to the scarce bacteriologic investigation and the low yield achieved in culturing pulmonary specimens. The study found under-register of cases and lack of precision in the information reaching the National Programme.
Subject(s)
Tuberculosis, Pulmonary/diagnosis , Adolescent , Argentina/epidemiology , Child , Child, Preschool , Diagnosis, Differential , Disease Notification , Gastric Lavage , Humans , Infant , Infant, Newborn , Sputum/microbiology , Tuberculosis, Pulmonary/epidemiology , Tuberculosis, Pulmonary/microbiologyABSTRACT
Confirming the diagnosis of pediatric tuberculosis is cumbersome, due to the clinical features (generally paucibacillary forms) of the disease. This national study was undertaken in order to establish: the features of childhood tuberculosis at the time of diagnosis, the criteria on which the pediatricians based the diagnosis, the bacteriologic contribution to the diagnosis and the quality of notifications to the National Programme. Medical and laboratory records were reviewed for children under 15 years of age who were diagnosed with tuberculosis disease or primary infection during 1995. The study included children cared for at health centres from Argentinean provinces (capital city excluded) where pediatricians accepted to participate. Four hundred cases (17
of childhood notifications to the National Programme) and 81 primary infections were studied. The percentage of children studied by means of chest radiology, presence of symptoms, Mantoux test, case contact investigation and bacteriology were 95.3
, 79.6
, 90.1
, 92.7
and 35
for pulmonary cases, respectively, and 87.7
, 100
, 87.7
, 85.9
and 78.9
for extra-pulmonary cases, respectively. Of the evaluated pulmonary cases, 99.1
had abnormal x-rays, 79.0
had a tuberculin test > or = 10 mm, 79.8
had symptoms and 80.2
had a history of close contact. All extra-pulmonary patients had symptoms at the time of diagnosis; 63.0
had abnormal chest radiograph at diagnosis. Bacteriologic confirmation was achieved in 10.7
of the cases (20.8
and 40.0
of the investigated pulmonary and extra-pulmonary cases, respectively). This study would indicate that the diagnosis is made at relatively early stages of the disease. In general, recommendations of the Argentine Society of Pediatrics were followed. A low rate of bacteriological proof of diagnosis was observed, probably due to the scarce bacteriologic investigation and the low yield achieved in culturing pulmonary specimens. The study found under-register of cases and lack of precision in the information reaching the National Programme.
Subject(s)
Laboratories/standards , Mycobacterium tuberculosis/isolation & purification , Sputum/microbiology , Tuberculosis/microbiology , Argentina , Bacteriological Techniques , False Negative Reactions , False Positive Reactions , Laboratories/organization & administration , Quality Control , Tuberculosis/prevention & controlABSTRACT
IgG antibody to Mycobacterium tuberculosis antigen 5 and tuberculin purified protein derivative (PPD) was measured, by enzyme-linked immunosorbent assay (ELISA), in serum samples from 86 patients with active pulmonary tuberculosis and 91 non-tuberculous control subjects from Santa Fé, Argentina. The geometric mean titre for the tuberculosis patients was 74.6 with antigen 5 and 99.5 with PPD. In 91 control subjects the geometric mean titres were 3.6 and 15.6 respectively. Titres were not related to tuberculin reactor status or prior BCG vaccination. At a serum dilution end-point of 1:40, ELISA with antigen 5 had a sensitivity of 81.4% and a specificity of 93.4% for tuberculosis. At 1:40, ELISA with PPD showed a sensitivity of 82.6% and a specificity of 54.9% for tuberculosis. Applied at a serum dilution of 1:40 to a hypothetical model population with a tuberculosis prevalence of 2%, ELISA using antigen 5 would correctly classify 93.2% of persons and ELISA with PPD, 55.5%. At a dilution of 1:80, accuracy is increased to 99.3% with antigen 5 and 83.3% with PPD, but sensitivity decreases to 64.0% with antigen 5 and 72.1% with PPD. Thus, antigen 5 is more accurate than PPD for the diagnosis of tuberculosis using ELISA.
