Diagnostic performance of adenosine deaminase activity in pleural fluid: a single-center experience with over 2100 consecutive patients

OBJECTIVE

To determine the diagnostic utility of adenosine deaminase (ADA) in a large series of pleural effusions of different etiologies.

METHODS

A retrospective study of 2104 consecutive patients presenting with pleural effusion was carried out at a Spanish university hospital. ADA levels in pleural fluid were determined using a non-Giusti automatic kinetic assay, and a receiver operating characteristics curve analysis was applied to estimate their discriminative properties.

RESULTS

Pleural tuberculosis (TB) accounted for 221 (10.5%) effusions. Pleural fluid ADA >35U/L yielded 93% sensitivity, 90% specificity, a positive likelihood ratio (LR) of 10.05 and a negative LR of 0.07 for the diagnosis of TB among lymphocytic exudates. The ADA activity was significantly higher in neutrophil- (111.6U/L) than in lymphocyte-rich (62.4U/L; p=0.002) TB effusions. Overall, more than 40% of parapneumonics and half of lymphomatous effusions exceeded the cutoff set for TB. These were the only causes of ADA activity above 250U/L. When the prevalence of TB as a cause of exudative effusions is low (e.g., 1%), the estimated positive predictive value of the ADA test may be as low as 7%, although the negative predictive value remains high (99.9%).

CONCLUSION

Where available, pleural ADA should be routinely used to rule TB in or out in areas with moderate to high or low TB prevalence, respectively. A high ADA level is a characteristic not only of lymphocytic, but also of neutrophilic TB effusions. An extremely high ADA activity should raise suspicion of empyema or lymphoma.

C-reactive protein: a sensitive marker in the management of treatment response in parapneumonic empyema of children

C-reactive protein (CRP) is one of the best indicators of the acute phase response to inflammation. The rapid kinetics of CRP metabolism appears to closely parallel the degree of inflammation. The purpose of this prospective study was to analyze the clinical value of CRP, erythrocyte sedimentation rate (ESR), and white blood cell count (WBC) in the assessment response to treatment in children with parapneumonic empyema. Thirty-eight children were prospectively studied. CRP was elevated in all patients on the day of hospital admission. With antibiotic treatment, serum CRP levels fell rapidly within the first days, and in 32 patients who had uncomplicated course, serial CRP levels fell progressively at each measurement. All but four patients had normal CRP levels on the day of hospital discharge. ESR was also elevated in all patients on the day of hospital admission. Despite antibiotic treatment, ESR continued to increase in all patients in the first few days, with peak values reached on day 3. Only three patients had normal ESR levels on the day of hospital discharge. In six patients who had a complicated course, after an initial decrease, CRP levels began to rise earlier than ESR and WBC count. Plasma CRP level is a sensitive marker not only in the diagnosis of parapneumonic empyema, but also in the management of treatment response.

Pleural fluid transforming growth factor-beta1 correlates with pleural fibrosis in experimental empyema

Transforming growth factor-beta1 (TGF-beta1) is a growth factor that is implicated in fibrosis of many organs. The purpose of this study was to determine the sequential levels of TGF-beta1 in the pleural fluid of rabbits that had undergone empyema induction, as fibrosis of the pleural space develops. Thirty-seven rabbits underwent empyema induction. Rabbits were sacrificed on Days 1, 2, 3, 4, 5, 6, and 8. Pleural fluid and viscera pleura specimens were collected at autopsy. TGF-beta1 levels were measured in pleural fluid using a commercially available ELISA kit, and pathologic specimens were scored for evidence of fibrosis (pleural thickness and number of fibroblasts). The median levels of pleural fluid TGF-beta1 increased from 8,100 pg/ml (Days 1 and 2) to 39,600 pg/ml (Day 8). Pleural fluid TGF-beta1 levels closely correlated with microscopic pleural thickness (r = 0.7, p < 0.001) and number of fibroblasts present in the visceral pleura (r = 0.68, p < 0.001). The first increase in pleural fluid levels of TGF-beta1 (Day 3) occurred before the increase in pleural thickness (Day 4) and before the increase in number of fibroblasts (Day 4). In conclusion, pleural fluid levels of TGF-beta1 rise in experimental empyema as pleural fibrosis develops. The rise in empyemic pleural fluid TGF-beta1 levels correlates with markers of pleural space fibrosis.

Inhibition of Candida albicans growth by calprotectin in the absence of direct contact with the organisms

Calprotectin is a calcium- and zinc-binding protein that is present in neutrophil cytoplasm and abscess fluid supernatants. This protein appears to inhibit microbial growth through competition for zinc; however, experiments to show that calprotectin can inhibit growth of microorganisms across filter membranes have yielded conflicting results to date. To prevent recontamination of the filtrate by zinc in this type of experiment, Candida albicans was cultured on filter membranes placed on top of an agarose gel containing calprotectin. In these studies, calprotectin in the gels underneath did suppress growth on top of the filters, an effect reversible by 30 microM ZnSO4. In other experiments, the protein did not adhere to the organisms and later suppress their growth. These results indicate that calprotectin inhibits C. albicans growth in the absence of direct contact with the organisms; the findings support a zinc-deprivation mechanism of antimicrobial activity for this protein.

Pleural fluid chemical analysis in parapneumonic effusions. A meta-analysis

Controversy exists regarding the clinical utility of pleural fluid pH, lactate dehydrogenase (LDH), and glucose for identifying complicated parapneumonic effusions that require drainage. In this report, we performed a meta-analysis of pertinent studies, using receiver operating characteristic (ROC) techniques, to assess the diagnostic accuracy of these tests, to determine appropriate decision thresholds, and to evaluate the quality of the primary studies. Seven primary studies reporting values for pleural fluid pH (n = 251), LDH (n = 114), or glucose (n = 135) in pneumonia patients were identified. We found that pleural fluid pH had the highest diagnostic accuracy for all patients with parapneumonic effusions as measured by the area under the ROC curve (AUC = 0.92) compared with pleural fluid glucose (AUC = 0.84) or LDH (AUC = 0.82). After excluding patients with purulent effusions, pH (AUC = 0.89) retained the highest diagnostic accuracy. Pleural fluid pH decision thresholds varied between 7.21 and 7.29 depending on cost-prevalence considerations. The quality of the primary studies was the major limitation in determining the value of pleural fluid chemical analysis. We conclude that meta-analysis of the available data refines the application of pleural fluid chemical analysis but a clearer understanding of the usefulness of these tests awaits more rigorous primary investigations.

Microorganisms and leukocytes in purulent sinusitis: a symbiotic relationship in metabolism

Since the exchange of gases, as well as metabolites, is greatly impeded in a paranasal sinus empyema, it is not unlikely that certain organic substances be retained and accumulated in purulent secretion. In this study, secretions aspirated from experimentally infected maxillary sinuses of 26 rabbits were analysed biochemically. Quantitatively, by far the most important acid accumulated in secretions was lactic acid. Lactate induces metabolic acidosis and exerts an inhibitory effect on mammalian defense mechanisms. Lactate may also be used as an energy source by certain microorganisms. In spite of its leukocytic origin lactic acid thus promotes the continuation of a bacterial infection. In addition, certain other organic acids of bacterial origin were found, which, in different ways, contribute to the impediment of antimicrobial defense functions.

The presence of platelet-activating factor associated with eosinophil and/or neutrophil accumulations in the pleural fluids

Platelet-activating factor (PAF) has been reported to play a role in the inflammatory reaction, but the mechanism of PAF in humans is still unclear. We examined the presence of PAF in pleural fluids from 23 patients with pleural effusion and in all cases detected PAF associated with eosinophil and/or neutrophil infiltrations. The amounts of PAF in pleural fluids were, respectively, 340, 50 to 170, and 1,250 to 2,130 fmol/ml for a patient with eosinophilic pneumonia, those with pneumothorax (n = 9), and empyema (n = 3). In contrast, patients with tuberculous pleuritis (n = 2), lung edema (n = 3), or malignant disease (n = 5) had no detectable amounts of pleural fluid PAF (less than or equal to 10 fmol/ml). The amount of PAF showed a close correlation with the numbers of eosinophils and neutrophils in the pleural fluids. Furthermore, PAF was mostly detected in the cellular fractions, and the molecular species of PAF from the patients with empyema were almost consistent with those of PAF generated by human blood neutrophils. These results indicate that neutrophils and, presumably, eosinophils were the cellular source of PAF in the pleural fluids in the pathologic state of inflammation.

Polyarticular Clostridium perfringens pyoarthritis

A woman with rheumatoid arthritis presented with an abdominal mass and Clostridium perfringens septic arthritis in both wrists and shoulders. We believed this to be the first reported case of polyarticular septic arthritis due to Clostridium perfringens. Apatite, lipid, and cholesterol crystals in the shoulder joint effusions were a potential source of diagnostic confusion.

C-reactive protein, sialic acid and adenosine deaminase levels in serum and pleural fluid from patients with pleural effusion

Laboratory analysis of pleural fluids is essential to determine underlying diseases. The authors evaluated the clinical significance of C-reactive protein (C-RP), sialic acid (SA), and adenosine deaminase (ADA) determinations in sera and pleural fluids from 37 patients with pleural effusion. (FP12)C-RP and sialic acid levels and ADA activities were higher in exudates than in transudates of pleural fluids. Serum and pleural fluid C-RP levels were high in patients with pyothorax. Determinations of serum sialic acid and the pleural fluid to serum ratio were useful for the differential diagnosis of pulmonary tuberculosis and malignancy. ADA activities of pleural fluid and serum are useful for the differentiation of malignancy from tuberculosis and nonspecific pyothorax. C-RP concentrations of pleural fluid correlated to serum levels. However, concentrations of sialic acid and ADA activities were not correlated to serum levels and only correlated to protein concentrations of pleural fluids.

Penetration of aminoglycosides in uninfected pleural exudates and in pleural empyemas

The concentrations of gentamicin, netilmicin, and amikacin were determined after one single intravenous injection in uninfected pleural fluid after thoracotomy and in purulent pleural empyemas. The mean peak concentrations in the pleural fluid after the injection of gentamicin (1.5 mg/kg), netilmicin (2.0 mg/kg), and amikacin (7.5 mg/kg) were 2.9 +/- 0.3 mg/L, 3.7 +/- 0.8 mg/L, and 11.0 +/- 3.1 mg/L, respectively. The pleural penetration of the drugs was very high (from 80.0 to 99.1 percent). By contrast, gentamicin and netilmicin were not detectable in empyema pus; in this exudate the mean peak level of amikacin was 5.7 +/- 2.2 mg/L, with the penetration of this drug being 31.0 percent. The concentrations of parenterally administered aminoglycosides are substantially lower in empyema pus than in sterile pleural fluid. The possibility of poor pleural penetration of some aminoglycosides, as well as the presence of local conditions in pleural empyema unfavorable to the bioactivity of these drugs, must be kept in mind when treating pleural infections.

Gas chromatographically quantitated lactate in empyema and other pleural effusions

To determine the value of gas chromatographically measured lactate in distinguishing between empyema and other causes of pleural effusion, consecutively collected samples of pleural fluid were studied. In 15 cases of empyema the mean lactate concentration was 11.60 mM and higher than in 41 patients with other diagnoses (mean 3.98 mM). The concentration of lactate remained unchanged during storage at 4 degrees C for two years. Gas chromatographic quantitation of lactate is useful in the presumptive diagnosis of empyema, and stability of the lactate concentration allows retrospective analyses.

Pleural fluid lactate in pleural effusion

Pleural fluid lactate (PFL) and blood lactate (BL) concentrations were simultaneously measured in samples from 46 patients with pleural effusion. PFL exceeded 6 mmol/l in all 15 patients with pyogenic bacterial pleurisy but in only 5 of the other 31 patients. We have found that a PFL-BL difference greater than or equal to 6 mmol/l has a sensitivity of 100% and a specificity of 93.8% in detecting pyogenic pleural effusions. Results are available within 1 h of sample collection, so that PFL-BL difference may become a useful aid in the early assessment of pleural effusions.

Pleural fluid ferritin concentrations in human disease

The concentration of ferritin was measured in the pleural fluid of 108 patients with pleural effusions. In all groups of patients the ferritin concentration was higher in pleural fluid than in serum. The greatest differences, with up to 100 times more ferritin in the pleural fluid, were found for patients with rheumatoid pleurisy, malignant effusions, and empyema. In patients with non-malignant inflammatory pleural effusions the concentration of ferritin in pleural fluid correlated significantly with other pleural fluid indices of inflammation: there was a positive correlation with lactate dehydrogenase activity and a negative correlation with concentrations of glucose and complement components C3 and C4. Ferritin was detected immunocytochemically only in the macrophages found among the pleural fluid cells. Our study shows that large amounts of ferritin accumulate locally in the pleural cavity in certain types of pleural inflammation. The accumulation is probably partly the result of increased local reticuloendothelial system activity. Determination of the concentration of ferritin in pleural fluid may provide corroborative information for differential diagnosis and may further our understanding of the pathogenetic events that lead to the perpetuation of inflammatory activity in pleural effusions.

Value of pleural lactate in the differential diagnosis between empyema and non-bacterial pleural effusions

Lactate concentrations in the pleural fluid of 50 patients were determined by the Monotest Lactate Kit. Lactate values were found higher in bacterial pleural infections than in cases of hydrothorax. Elevated levels were also found in most cases of histologically confirmed cases of pleural neoplasms and in some cases of non-bacterial pleuritis exsudativa . The highest levels were found in cases of empyema, but there was considerable overlapping between the groups. Pleural lactate thus appears to have little diagnostic value in the differential diagnosis between empyema and non-bacterial pleural effusions.

Elevated pleural fluid pH in Proteus mirabilis empyema

Three cases of Proteus empyema were associated with elevated pleural fluid pH values. The elevated pH is likely due to ammonia production by Proteus organisms.

[Osmometry as a method of control of homeostasis in acute suppurative destructive diseases of the lung and pleura]

The osmolar status was studied in 63 patients with acute abscesses of lungs and empyema of pleura at different stages of the conservative and operative treatment. The hypoosmolarity syndrome was revealed at the acute stage of the disease against the background of a pronounced purulent intoxication. An increased excretion of nonidentified osmotically active metabolites with urine was registered at the height of pyodestructive process and postoperative disease.

Muscle and plasma amino acids following injury. Influence of intercurrent infection

The present study was undertaken to determine intracellular amino acid patterns in patients with multiple trauma, whether or not complicated by sepsis and during convalescence. A percutaneous muscle biopsy was performed three to four days following major accidental injury in ten patients and analyzed for muscle free amino acids. Venous blood was drawn at the time of the biopsy and analyzed for plasma free amino acids. Five patients developed sepsis and a repeat biopsy was performed on days 8 to 11. In five of the patients a biopsy was performed during the late convalescent period (anabolic phase). A marked depletion of nonessential amino acids in muscle occurred in both injury and sepsis due to a decrease (50%) in glutamine, which was equally marked in both states. The essential amino acids in muscle increased in injury. During sepsis, a further increase was observed with a return toward normal in the convalescent period. In injury, the most marked rise was in the branched-chain amino acids, phenylalanine, tryosine and methionine. With sepsis, a further rise in muscle branched-chain amino acids, phenylalanine and tryosine occurred, while plasma levels remain unchanged. During convalescence, muscle glutamine, arginine, histidine and plasma branched-chain amino acids were below normal, whereas muscle phenylalanine and methionine were elevated. The muscle free amino acid pattern observed after major trauma was essentially the same as earlier described following elective operation. This suggests a common response of intracellular amino acids irrespective of the degree of injury, and may indicate that the pump settings which regulate amino acid transport follow the "all or none" rule. The high intracellular levels of branched-chain amino acids in sepsis suggest that the energy deficit of this state is due to an impairment of substrate use rather than intracellular availability. The high concentrations of the aromatic amino acids and methionine may be due to altered liver function. During the late convalescent period (anabolic phase) the low levels of certain key amino acids suggests inadequate nutrition. The difficulties in nourishing the injured or septic patient are well recognized. The period following these catabolic states may be an important period for the application of an optimal, aggressive nutritional regimen.

[Tuberculous pleural effusion and pleural effusion secondary to non-specific bacterial infection: biochemical differential diagnosis (author's transl)]

The authors study 14 different analytical parameters in the pleural fluid in order to recognize differential biological criteria, helping to establish an etiologic diagnosis in patients with suggestive clinical symptoms and biological data of an infectious process. In a group of 38 patients with bacterial exudative pleural effusion (22 of tuberculous origin and 16 secondary to non-specific bacterial infection), the following parameters were analyzed: total proteins, acid glucoprotein, X1, antytripsin, CDH, acid phosphatase, amylase, cholinest, copper, iron, pCO2, pO2 pH, glucose, and cholesterol. The results of amylase, copper, pCO2, pO2 and pH determinations in the pleural fluid show statistical significant differences between the tuberculous cases and the patients with non-specific infections. Lastly, the authors mention the minimal biological criteria necessary to confirm the tuberculous or non-specific bacterial etiology of a pleural fluid, stressing the value of the levels of cholinesterase, copper, pO2 and pH as differential data.