The diagnostic accuracy of pericardial and urinary lipoarabinomannan (LAM) assays in patients with suspected tuberculous pericarditis.

We evaluated the diagnostic accuracy of urinary and pericardial fluid (PF) lipoarabinomannan (LAM) assays in tuberculous pericarditis (TBP). From October 2009 through September 2012, 151 patients with TBP were enrolled. Mycobacterium tuberculosis culture and/or pericardial histology were the reference standard for definite TBP. 49% (74/151), 33.1% (50/151) and 17.9% (27/151) of patients had definite-, probable-, and non-TB respectively; 69.5% (105/151) were HIV positive. LAM ELISA had the following sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value and negative predictive values (95% confidence interval): urinary - 17.4% (9.1-30.7), 93.8% (71.7-98.9), 2.8 (0.1-63.3), 0.9 (0.8-0.9), 88.9% (56.5-98.0), and 28.3% (17.9-41.6); PF - 11.6% (6.0-21.3), 88% (70.0-95.8), 0.9 (0.08-12.0), 1.0 (0.9-1.1), 72.7% (43.4-90.1), and 26.6% (18.2-36.9). Sensitivity increased with a CD4 ≤ 100 cells/mm(3) from 3.5% to 50% (p < 0.001) for urinary LAM ELISA; for urinary LAM strip test, grade 1 and 2 cut-points performed similarly, irrespective of HIV status or CD4 count. For PF LAM strip tests, switching cut-points from grade 1 to 2 significantly reduced test sensitivity (54.5% versus 19.7%; p < 0.001). Urinary and PF LAM assays have low sensitivity but high specificity for diagnosis of TBP. The sensitivity of urinary LAM is increased in HIV-infected patients with a CD4 ≤ 100 cells/mm(3).

Poor Penetration of Antibiotics Into Pericardium in Pericardial Tuberculosis.

Pericardial tuberculosis (TB) is associated with high therapy failure and high mortality rates. Antibiotics have to penetrate to site of infection at sufficient non-protein bound concentrations, and then enter bacteria to inhibit intracellular biochemical processes. The antibiotic concentrations achieved in pericardial fluid in TB pericarditis have never been measured before. We recruited two cohorts of patients with TB pericarditis, and left a pigtail catheter in-situ for serial drug concentration measurements over 24 h. Altogether, 704 drug concentrations were comodeled for pharmacokinetic analyses. The drug concentrations achieved in pericardial fluid were compared to the minimum inhibitory concentrations (MICs) of clinical Mycobacterium tuberculosis isolates. The total rifampicin concentration pericardial-to-serum ratios in 16 paired samples were 0.19 ± 0.33. The protein concentrations of the pericardial fluid in TB pericarditis were observed to be as high as in plasma. The non-protein bound rifampicin concentrations in pericardial fluid were 4-fold lower than rifampicin MICs in the pilot study, and the peak concentration was 0.125 versus 0.208 mg/L in the second (p = 0.001). The rifampicin clearance from pericardial fluid was 9.45 L/h versus 7.82 L/h in plasma (p = 0.002). Ethambutol peak concentrations had a pericardial-to-plasma ratio of 0.55 ± 0.22; free ethambutol peak concentrations were 2.30-lower than MICs (p < 0·001). The pericardial fluid pH was 7.34. The median pyrazinamide peak concentrations were 42.93 mg/L versus a median MIC of 800 mg/L at pH 7.34 (p < 0.0001). There was no significant difference between isoniazid pericardial fluid and plasma concentrations, and isoniazid peak concentrations were above MIC. This is the first study to measure anti-TB drug concentrations, pH and protein in the pericardial TB fluid. Pericardial concentrations of the key sterilizing drugs for TB were below MIC, which could contribute to poor outcomes. A new regimen that overcomes these limitations might need to be crafted.