Extensive Mycobacterium tuberculosis circulation in a highly endemic prison and the need for urgent environmental interventions.

Aimed at assessing the circulation of Mycobacterium tuberculosis in a highly endemic prison, this 13-month prospective study was performed on strains isolated from tuberculosis (TB) cases detected passively and actively. We used X-ray screening of newly admitted inmates and mass screening at the beginning of the study and again 1 year later. Of the 94 strains genotyped by restriction fragment-length polymorphism, 79 (84·0%) belonged to one of the 12 identified clusters (2-21 strains each), including two main clusters (18 and 21 cases, respectively). A history of TB treatment was reported in 22/79 (27·8%) clustered cases. Time-space distribution of clustered cases was predominantly consistent with transmission, in micro-epidemics. Given the dominant pattern of exogenous infection and the extensive strain circulation, effective TB control should emphasize reduction of overcrowding and improvement of environmental measures as a complement to detection and treatment of cases.

Immunological diagnosis of tuberculosis based on recombinant antigens ESAT-6 and CFP-10 in children from an endemic area in northeast Brazil.

Diagnostic tests for tuberculosis (TB) using interferon gamma (IFN-γ) responses produced by T lymphocytes after stimulation by early secretory antigen target 6 (ESAT-6), culture filtrate protein 10 (CFP-10) or purified protein derivate (PPD) were carried out using ELISA (enzyme-linked immunosorbent assay) in whole blood culture supernatants from children with suspected TB disease (n=21), latent TB infection (LTBI; n=17) and negative controls (NC; n=21) from Recife, Pernambuco, Brazil. The results were analysed using the ROC (receiver operating characteristic) curves and the areas under the curve (AUC) generated varied from 0.5 to 1.0 with higher values indicating increased discriminatory ability. Comparisons of AUCs were made using non-parametric assumptions, and the differences were considered significant if P<0.05. The ROC curve showed a statistical difference (P = 0.015) between the LTBI and NC groups with an AUC of 0.731, TB disease and NC (AUC=0.780; P=0.002) and a group with TB (latent infection+disease, n=38) and NC (AUC=0.758; P = 0.001) when the antigen used was ESAT-6. No statistical difference was found between the groups when CFP-10 or PPD was used. In conclusion, the ESAT-6 test may be the most appropriate for diagnosis of childhood TB, both LTBI and TB disease, when associated with epidemiological and clinical data, especially in endemic areas such as Brazil.

IgA antibody responses to Mycobacterium tuberculosis recombinant MPT-64 and MT-10.3 (Rv3019c) antigens in pleural fluid of patients with tuberculous pleurisy.

SETTING: Microbiological tests lack sensitivity for pleural tuberculosis (TB) and histopathology is expensive, time consuming and needs specialised personnel. Immunoassay (ELISA) may be a promising approach in this respect. OBJECTIVE: To evaluate the reactivity of IgA antibody to MPT-64 and MT-10.3 recombinant mycobacterial protein antigens in pleural fluid as a marker of pleural TB, based on the fact that IgA is the main antibody in the mucosa/serosa of the gastrointestinal and respiratory tract. METHOD: Anti-MPT-64 and MT-10.3 IgA response was determined by ELISA in 72 patients with pleural TB and 27 with other pleural conditions. RESULTS: High sensitivities for IgA were measured against MPT-64 (52/72, 72%) and MT-10.3 (52/72,72%) antigens. Combining the sensitivities of both antigens, further increase in sensitivity (55/72, 76%) was obtained with no loss of specificity (96%). Similar IgA reactivity was obtained from culture-negative and culture-positive specimens. In eight pleural TB patients with human immunodeficiency virus (HIV) co-infection, the sensitivity was 88% (7/8). CONCLUSION: To our knowledge, this is the first description of the presence of IgA antibody pleural TB effusion reactive to MPT-64 and MT-10.3, with sensitivity similar to histopathological examination, which is presently considered the gold standard for pleural TB.

Mediators of arachidonic acid-induced contractions of indomethacin-treated guinea-pig airways: leukotrienes C4 and D4.

Arachidonic acid (AA) (66 microM) induced contractions of indomethacin-treated (8.4 microM) guinea-pig tracheal and lung parenchymal preparations. Mepacrine (210 microM) treatment did not affect the magnitude of contraction induced by AA. Normal and ovalbumin-sensitized tissues responded identically to AA, and released equivalent amounts of the contractile mediators. Nordihydroguaiaretic acid (100 microM) markedly reduced release of the contractile mediators and reduced AA-induced contractions of the airways. The mediators of AA-induced, calcium ionophore A23187-induced, and antigen-induced contraction of the trachea and lung parenchyma were purified and identified by reverse-phase high performance liquid chromatography to be leukotrienes C4 and D4, being present in an approximate ratio of 20:1. Mepacrine-treated trachea exhibited a smaller contractile response to stimuli (A23187 for normal tissues and ovalbumin for sensitized tissues). Addition of exogenous AA (66 microM) increased the magnitude of contraction, although not to the level observed on tissues not treated with mepacrine. There was no observable effect of AA on the response of mepacrine-treated parenchyma to the ionophore or antigen. It was concluded that (a) immunological sensitization does not alter AA metabolism via the lipoxygenase pathway in guinea-pig airways and (b) the mediators of AA-induced contraction are leukotrienes C4 and D4.

Bronchodilator-mediated relaxation of normal and ovalbumin-sensitized guinea-pig airways: lack of correlation with lung adenylate cyclase activation.

Isoprenaline, vasoactive intestinal peptide (VIP), prostaglandin E2 (PGE2) and forskolin caused a dose-dependent relaxation of normal and ovalbumin-sensitized guinea-pig tracheal spirals and lung parenchymal strips in vitro. There was no difference in magnitude of relaxation or sensitivity to these relaxants between normal and sensitized tissues. The rank order of potency (concentration of each drug at which 50% of the maximum is obtained) for these relaxants on both trachea and parenchyma was VIP greater than isoprenaline greater than PGE2 greater than forskolin, although the parenchyma was more sensitive than the trachea. The rank order of efficacy of the drugs used in relaxing both the trachea and lung parenchyma was isoprenaline (10 microM) greater than forskolin (30 microM) greater than VIP (0.1 microM) greater than PGE2 (10 microM). PGE2 at concentrations greater than 1 microM sometimes contracted the lung strip. Pretreatment with indomethacin (8.5 microM), a cyclo-oxygenase inhibitor, reduced the resting tone of tracheal spirals, but did not significantly affect the tone of lung strips. Indomethacin-pretreatment did not affect drug-induced relaxations of either normal or sensitized tracheal spirals. However, both normal and sensitized indomethacin-pretreated lung strips relaxed significantly less (P less than 0.05) to isoprenaline, PGE2 and forskolin. Indomethacin-pretreatment did not affect sensitivity of normal and sensitized trachea or parenchyma to the relaxant drugs. All the relaxant drugs used stimulated adenylate cyclase activity in normal or sensitized lung parenchyma membrane preparations. The rank order of efficacy (maximal activation) was forskolin greater than isoprenaline = VIP greater than PGE2. There was no difference in response between normal and sensitized lungs. Adenylate cyclase activity of normal lung was stimulated as follows: forskolin (100 microM), 500.0 +/- 50.0%; isoprenaline (100 microM), 186.0 +/- 29.0%; VIP (10 microM), 213.0 +/- 19.0% and PGE2 (100 microM), 155.0 +/- 23.0% of basal activity. Similar values were obtained for sensitized lung parenchyma. Indomethacin-pretreatment did not significantly affect normal or sensitized lung adenylate cyclase stimulation by isoprenaline, VIP, forskolin or PGE2. It was concluded that: Immunological sensitization to ovalbumin does not induce hypoactivity of relaxant drug receptors and/or the adenylate cyclase system of the airway tissues of the guinea-pig. (b) There is an apparent lack of correlation between tissue relaxation in vitro and adenylate cyclase activity since the rank order of the efficacy of a range of relaxants was different for the two effects and furthermore indomethacin-treatment of airway tissues yielded differential results.

Role of calcium in arachidonic acid-induced contractions of guinea pig airways.

We have previously shown that arachidonic acid (AA)-induced contractions of indomethacin-pretreated guinea pig trachea and parenchyma are due to the synthesis of leukotrienes C4 and D4. The present experiments were designed to investigate the role of calcium (Ca2+) in the above. AA (66 microM)-induced contractions of trachea, but not parenchyma, were reduced in Ca2+-free Krebs-Henseleit solution ( KHS ). However the contractions of both trachea and parenchyma were abolished in Ca2+-free KHS with either lanthanum chloride (1 mM) or EDTA (300 microM). The Ca2+ antagonists, verapamil (100 microM), nitrendipine (100 microM), and TMB-8 (100 microM), reduced AA-induced contractions of both trachea and parenchyma. Re-addition of Ca2+ (2.2 mM) to trachea and parenchyma in Ca2+-free KHS in the presence of lanthanum restored the AA-induced contractions. This effect of Ca2+ was reduced by verapamil (100 microM) or nitrendipine (100 microM). LTC4-induced contractions of trachea and parenchyma were unaffected by nitrendipine (100 microM), whereas tracheal contractions were reduced in Ca2+-free KHS . Both tracheal and parenchymal contractions to LTC4 were reduced in Ca2+-free KHS in the presence of lanthanum chloride (1 mM). We conclude that superficially bound pools of Ca2+ are important in AA-induced contractions of the airways. Furthermore, nitrendipine reduces AA-induced contractions by inhibiting AA metabolism and not by inhibiting airway smooth muscle contraction induced by released leukotrienes.

Mycobacterium tuberculosis lipid antigens: use of multi-antigen based enzyme immunoassay for free and complex dissociated antibodies.

OBJECTIVE: To test the sensitivity and specificity of four lipid antigens of Mycobacterium tuberculosis: BDA-TDA, DAT, SL-I, and PIMs, adsorbed in the same microplate well, to detect reactive IgG by enzyme-immunoassay (EIA) from plain serum (MA-EIA) and dissociated immune complexes (ICMA-EIA). DESIGN: IgG antibodies against four antigens, placed in the same microplate well, were evaluated in serum from 155 tuberculous (TB) cases non-infected with the human immunodeficiency virus (HIV): 78 patients with positive bacilloscopy and culture, 33 patients with positive culture and 44 patients diagnosed by clinical and radiological criteria; and from 211 HIV negative control subjects: 32 patients with other pulmonary diseases, 100 healthy people and 79 close contacts. RESULTS: MA-EIA had an overall sensitivity and specificity of 61% (94/155) and 95% (200/211), respectively. We further examined whether the dissociation of immune complexes increases the number of positive reactions in those initially found to be seronegative (SN). The subset of 112 (76 controls and 36 TB) MA-EIA SN samples tested using ICMA-EIA yielded an overall sensitivity and specificity of 83% and 100%. The ICMA-EIA results improved the overall sensitivity from 61 to 80% without changing specificity. CONCLUSION: These preliminary results suggest that MA-EIA followed by ICMA-EIA, for SN samples, might serve as a fast, cheap, and easy method for the diagnosis of TB in less than 48 hours.

Mycobacterium tuberculosis typing: usefulness of DRE-PCR to confirm cross-contamination in the mycobacteriology laboratory of a general reference hospital for AIDS.

In this study two molecular typing methods, a simple double repetitive element PCR-based assay and the standardized restriction fragment length polymorphism (RFLP), were used to confirm cross-contamination in the mycobacteriology laboratory. Clinical specimens from 12 patients, submitted for acid-fast bacilli stain smear and processed for culture in Lowenstein-Jensen on the same day, resulted in positive bacterioscopy (+++) and confluent growth only for one of the patients. The specimens from all the other patients but two were smear-negative and culture-positive, with one or two colonies. None of them had clinical symptoms and radiological findings for active tuberculosis (TB). The suspicion of false-positive cultures arose when a health care worker who had had a PPD skin test conversion, claimed to be healthy and had no TB symptoms, was found to have a positive sputum culture. DRE-PCR demonstrated that all nine cultures typed belonged to one cluster, further confirmed by RFLP. Although DRE-PCR has been found to be poorly reproducible, it has enough discriminatory power to be useful for rapid epidemiological investigation in selected settings.

RFLP patterns and risk factors for recent tuberculosis transmission among hospitalized tuberculosis patients in Rio de Janeiro, Brazil.

Isolates of Mycobacterium tuberculosis from 120 tuberculosis patients seen in the 12 months ending September 1994 at 2 tertiary-care centres in Rio de Janeiro were characterized by IS6110 restriction fragment length polymorphism (RFLP) analysis. Ninety-seven patients (81%) had isolates with unique RFLP patterns, while 23 patients (19%) had isolates that belonged to 11 different RFLP cluster patterns. The strains from the latter patients were distributed among 1 group of 3 patients and 10 groups of 2 patients each. The cluster-pattern strains were not associated with gender, age, HIV infection, type of residence, living in shelter, homelessness or previous history of tuberculosis. However, clustering was strongly associated with multidrug resistance (P = 0.006). These data suggest that recent exogenous transmission may be important for the development of new cases of multidrug-resistant disease in patients attending tertiary-care centres in Rio de Janeiro, Brazil.

The usefulness of serum adenosine deaminase 2 (ADA2) activity in adults for the diagnosis of pulmonary tuberculosis.

Rapid diagnosis of Mycobacterium tuberculosis remains an obstacle for therapy of tuberculosis (TB). Adenosine deaminase isoform 2 (ADA2) is produced by activated macrophages and has been used for diagnosis of TB from extra-pulmonary sites. However, few studies adequately address whether serum ADA2 activity is useful for diagnosis of active pulmonary tuberculosis (PTB). We prospectively measured serum ADA2 activity in 110 patients with pulmonary disease (65 cases with active PTB and 45 cases with other respiratory diseases) and 78 healthy volunteers (eight with tuberculin skin test positive). The serum ADA2 for the diagnosis of PTB had the sensitivity of 36.9%, the specificity of 84.5%, the positive predictive value of 10.9% and the negative predictive value of 96.2%. We concluded that serum ADA2 activity is neither useful to diagnosis of active PTB nor to differentiate from other respiratory diseases.

IS1245 genotypic analysis of Mycobacterium avium isolates from patients in Brazil.

OBJECTIVE: Disseminated Mycobacterium avium infection is an emerging opportunistic disease among patients with acquired immunodeficiency syndrome (AIDS) in Brazil. The mode of transmission of M. avium in a developing country setting needs to be better characterized. METHODS: Mycobacterium avium strain collections in São Paulo and Rio de Janeiro were analyzed according to the strains' IS1245 DNA gel electrophoretic migration patterns. Medical records of the patients from whom M. avium isolates were available were reviewed, and their demographic characteristics were stratified according to the isolates' IS1245 DNA fingerprint patterns. RESULTS: Of 105 patients, 33 (31%) with M. avium isolated between 1990 and 1994 had strains having IS1245 patterns identical in patterns seen in isolates from two or more patients (designated as cluster pattern strains). Cluster pattern strains were isolated from 21 (39%) of 54 patients with disseminated infection (defined as infection due to M. avium isolated from a sterile site in an adult patient). Six of the cluster pattern strains were isolated only from sterile sites. In São Paulo, cluster pattern strains were significantly more likely to be isolated from patients with disseminated disease. CONCLUSIONS: These preliminary observations suggest that in large cities of Brazil, a high proportion (at least 39%) of disseminated M. avium infections in patients with AIDS results from a recent transmission. Some strains of M. avium may be more likely to cause disseminated disease than others after an infection.

Detection of IgA anti-PGL-I specific antigen to Mycobacterium leprae in mangabey monkeys inoculated with M. leprae.

Using sera from 4 pairs of mangabey monkeys inoculated with titrated doses of Mycobacterium leprae we demonstrated that IgA antibodies against M. leprae specific PGL-I antigen were present in 75% of inoculated monkey's sera. High IgA antibody was detected in 50% (3/6) of infected animals and all three developed lepromatous leprosy (LL). Antibody titers correlated with PGL-I antigen in serum. The highest IgA peak appeared late and corresponded to the beginning of treatment, and in two of them appeared shortly after or corresponded with neurological damage. Low IgA response was found in the other 3 monkeys (50%-3/6), two of which developed indeterminate leprosy (I) and the other one LL. Low IgA levels appeared late after IgG and IgM, and shortly after neurologic signs. Both I monkeys were negative for PGL-I in serum. The remaining 2 monkeys (25%-2/8) did not show an IgA response; one of them developed LL but the disease regressed to I. IgM seemed to correspond to the appearance of PGL-I in serum. The other animal did not develop clinical symptoms of leprosy, and PGL-I in serum was negative. Although there was no clear relation between the development of anti-PGL-I IgA and experimental leprosy, the finding of a high IgA response in some animals suggests that further studies are needed to evaluate the role of antigen-specific IgA in the disease process.

Borderline--tuberculoid leprosy: clinical and immunological heterogeneity.

The authors analysed some immunological criteria in leprosy patients diagnosed as borderline tuberculoid by the presentation of different grades of skin lesions as well as different grades of nerve involvement. Only 50% of the patients presented a single skin lesion and 58% had none or only one affected nerve. Nineteen patients (39.6%) showed a positive lepromin reaction (induration > or = 5 mm). Patients with a positive skin test had a greater number of skin lesions when compared with patients with a negative lepromin test. Fifty-seven percent of the patients were found to be positive using a lymphoproliferation test (LTT) in response to Mycobacterium leprae antigens. Positive LTT results did not correlate with the number of skin lesions, but patients unresponsive to LTT had a lesser extent of nerve involvement. Four out of 18 patients (22%) released high IFN gamma levels in PBMC culture stimulated by M. leprae. (mean U/ml +/- SD = 142 +/- 72). All of these 4 patients presented only one skin lesion, although three of them had more than one affected nerve. Nineteen out of 21 patients (90.5%) showed no anti-PGL-1 antibodies in their serum. The low levels of anti-PGL-1 antibodies among these patients confirmed their tuberculoid background even in those with multiple skin lesions. These findings seem to attribute an important role to IFN gamma in restraining the spreading of the infection in the skin, but IFN gamma may have an opposite effect on the nerves. The potential pathological effects of IFN gamma during the delayed type of hypersensitivity can be related to its ability to synergise with other inflammatory cytokines such as TNF alpha, IL-1 beta, and others.

Use of the anti-PGL-I antibody ELISA and the Mitsuda reaction in early diagnosis of leprosy.

Cutaneous reaction to the Mitsuda antigen and anti-PGL-I IgM antibodies (ELISA) were determined in 134 leprosy patients, 290 household contacts, 52 healthy controls and 43 tuberculous individuals. The multibacillary patients did not develop cell-mediated immunity (CMI), although they presented high levels of IgM (absorbance at 492 nm greater than 0.5). The paucibacillary patients presented CMI, although in varying degrees, and IgM levels did not exceed 0.5 absorbance units. Most of the contacts (107) showed a Mitsuda-positive test, and 25 of them were anti-PGL-I IgM seropositive (absorbance less than 0.5 but greater than 0.22), although none became ill during the two-year follow-up. Of the 17 Mitsuda-negative contacts, two exhibited an immunological status of lepromatous leprosy (negative Mitsuda test and positive serology; absorbance greater than 0.5) and became ill (one borderline lepromatous and one indeterminate leprosy). These results show that the immunological status of lepromatous leprosy can appear prior to clinical symptoms, and thus serology for anti-PGL-I IgM together with the Mitsuda test can be useful in an active search for new preclinical cases among high risk populations.

The dot-ELISA test for the detection of anti-PGL-1 IgM in leprosy patients and their contacts.

1. Since dot-ELISA has recently been reported to be a sensitive, simple and fast method, we have compared it with the conventional microplate ELISA method. Sera of 124 leprosy patients, 136 household and professional contacts, and 92 controls were tested for antibodies against a Mycobacterium leprae antigen using dot-ELISA on nitrocellulose membrane filters and microplate ELISA. 2. The sensitivity of the two techniques was similar for multibacillary patients, but dot-ELISA was less sensitive for paucibacillary patients although it was more specific (100%) than ELISA (93.4%). 3. Of 21 household contacts that gave a response by ELISA, 3 were also positive by dot-ELISA; one of these 3 developed indeterminate leprosy 12 months later and the other was diagnosed as borderline lepromatous after 28 months. 4. These data indicate that dot-ELISA has a high specificity and can be a useful tool in field evaluation.

Relationship between immune response and clinical manifestations in patients with tuberculosis.

Cutaneous reactivity to purified protein derivative (PPD) and antibody levels were investigated in 122 adults and 28 children with tuberculosis. IgG anti-PPD levels (measured by ELISA and reported as absorbance at 405 nm) were higher in adult patients with the disease for more than one year (0.533 +/- 0.391, N = 38 vs 0.224 +/- 0.256, N = 50 in patients with the disease for less than one year) as well as in children with disseminated tuberculosis (0.138 +/- 0.137, N = 11, vs 0.072 +/- 0.055, N = 15 in children with localized disease). The cut-off values (mean + 2SD) for healthy children and adults were 0.09 and 0.22 absorbance at 405 nm. In both adult and pediatric patients, cutaneous reactivity to PPD was inversely correlated with antibody levels. The present data provide additional evidence for the existence of an unstable spectrum of immune response in tuberculosis patients in whom changes in clinical situation are dynamic.

[Relationship between serological diagnosis (ELISA) and severity of pulmonary tuberculosis in children]. / Relação entre o diagnóstico sorológico (ELISA) e a gravidade da tuberculose pulmonar na infância.

Forty eight children from 0 to 13 years old were submitted to the enzyme-linked immunosorbent assay (ELISA) serological test with a view to detect anti PPD IgG antibodies, for diagnosis of pulmonary tuberculosis and to establish the relationship between immune response and radiological gravity of pulmonary tuberculosis (mild, moderate and severe). There were 29 children with pulmonary tuberculosis and 19 children without tuberculosis. The median ELISA optical density were: 0.098 in children with primary complex (mild); 0.092 in children with pneumonic pattern (moderate) and 0.134 in children with miliary tuberculosis (severe). These data show higher positive serological test results in severe forms of pulmonary tuberculosis (p = 0.0007).

Phenotypic and genotypic variant of MDR-Mycobacterium tuberculosis multiple isolates in the same tuberculosis episode, Rio de Janeiro, Brazil.

Assuming that the IS6110-restriction fragment length polymorphism (RFLP) changes at a constant rate of 3.2 years, this methodology was applied to demonstrate, for the first time, variant patterns of Mycobacterium tuberculosis (MTB) in multiple isolates obtained at short time intervals from sputum and blood of an HIV+ patient with multiple admissions to the Emergency Room and to the multidrug-resistant tuberculosis (MDR-TB) Reference Center of a secondary-care hospital in Rio de Janeiro, Brazil. In sputum, the IS6110-RFLP appeared in isolates with two variant patterns with 10 and 13 IS6110 copies. However, blood presented only the pattern corresponding to 10 copies, suggesting compartmentalization. With regard to the exact match of 10 of 13 bands, this may be a subpopulation with the same clonal origin and this may be related to the IS6110 transposition. A susceptibility test demonstrated an MDR profile (INH(R), RIF(R), SM(R), and EMB(R), with the sputum isolate also exhibiting EMB(S) (R = resistant; S = sensitive). A gene mutation confirmed resistance only to streptomycin. There was agreement between the results of the phenotypic test and the clinical response to MDR-TB treatment, suggesting serious implications with regard to treatment administration based exclusively on molecular methods, and calling attention to the fact that more effective control strategies against the emergence of MDR strains must be implemented by the TB control program to prevent transmission of MDR-MTB strains at health facilities in areas highly endemic for TB.

Pleural fluid ADA, IgA-ELISA and PCR sensitivities for the diagnosis of pleural tuberculosis.

The diagnosis of pleural tuberculosis (pTB) is difficult, and more sensitive and specific techniques are needed. In the period August 1998 to November 2002, we evaluated 132 patients with a pleural effusion submitted to a thoracentesis and pleural biopsy in a tertiary care hospital in Rio de Janeiro, Brazil. Three tests were performed and compared in the pleural fluid: ADA activity measurement, IgA-ELISA for two combined specific Mycobacterium tuberculosis antigens, and polymerase chain reaction (PCR) for detection of M. tuberculosis DNA. Ninety-five patients (72%) were given a final diagnosis of pTB. Overall histopathologic sensitivity was 77%. The sensitivities of pleural fluid culture and AFB smear were 42% and 1%, respectively. Twenty-one (22%) additional patients had a clinical diagnosis of pTB. Median follow-up time of all TB patients after the completion of antituberculous treatment was 13 months. Sensitivities of ADA, IgA-ELISA and PCR were 91%, 78% and 82%, while specificities were 93%, 96% and 85%, respectively. Only ADA sensitivity was significantly higher than the histopathologic examination (McNemar chi2 test; p = 0.002) and also significantly higher than ELISA (p = 0.049), but not higher than PCR (p = 0.143). We conclude that the routine use of ADA activity measurement in pleural fluid can obviate the need for a pleural biopsy in the initial diagnostic approach to pleural effusions, while IgA-ELISA and PCR techniques, potentially more specific tests, need further refinement to improve their accuracy.