Pleural fluid. creatinine - urinothorax haematocrit -haemothorax bilirubin gut perforation. Fluid samples 1st Plain Universal ( cell count)

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1 Examination Purpose of test Sample Fluid Profile (appearance, culture, WBC differential, ph, total protein, glucose, amylase, triglyceride, albumin, HDL) Peritoneal/ascitic and pleural fluid are the most common fluids received by the laboratory for analysis of biomarkers and are clinically valuable when used appropriately Pleural fluid The BTS recommendations state that there is no requirement to test bilateral effusions which, in the clinical setting, are strongly suggestive of a transudative process unless there are atypical features or a failure to respond to treatment If the supernatant from a turbid or milky fluid is clear, then empyema is likely and if the sample remains turbid, triglyceride measurement will help to identify a chylothorax. If clinically indicated contact laboratory to discuss the addition of the following tests: creatinine - urinothorax haematocrit -haemothorax bilirubin gut perforation ASSLD guidelines indicate that ph, lactate, tumour markers and other enzymes are unhelpful Please note that for culture the fluid should be inoculated into blood culture bottles at the bedside. Patients undergoing large volume paracenteses require cell count with differential only; culture not routine Fluid & blood Sample Tube/Container Fluid samples 1st Plain Universal ( cell count) 2nd Red top tube 6 ml (SAAG, TP, creatinine, triglycerides/cholesterol, amylase, glucose) 1 blood gas syringe (ph)>1ml (exclude air and send to laboratory within 30 minutes) Blood culture bottle (culture) Send samples for cell count and cultures to microbiology Send 2nd sample and blood gas syringe to biochemistry Blood samples Yellow Gel or Green Li Heparin Gel ( SAAG, protein Page 1 of 6

2 LDH,creatinine, amylase) Sample Volume Special Precautions Request Form: Laboratory Biological reference range Fluoride EDTA (glucose) 10ml fluid 4ml blood It is also important for laboratories to undertake a local risk assessment to address any health and safety issues related to handling potentially infective samples. Fluid samples pose a high risk, especially in query TB cases Clinical Chemistry & Haematology Requests Biochemistry and Microbiology Appearance and associated conditions - straw coloured = normal - cloudy = high neutrophils - milky = chylous - blood stained = TB/ malignancy/trauma - tea coloured =pancreatitis - food particles =oesophageal rupture - 'anchovy sauce like' = ruptured amoebic abscess - green/brown= biliary tract disease Peritoneal/Ascitic Fluid Serum ascites albumin gradient (SAAG) SAAG= Serum albumin- ascites fluid albumin SAAG >11g/L is associated with portal hypertension (transudate) a high gradient is associated with diffuse parenchymal liver disease and occlusive portal and hepatic venous disease (as well as nephrotic syndrome, liver metastasis and hypothyroidism) SAAG<11g/L is associated with tuberculosis peritonitis, chylous ascites, peritoneal carcinomatosis, pancreatic or biliary inflammation, nephotic syndrome, bowel obstruction/infarction. The presence of 250 polymorphonuclear cells (PMN) per mm³ is diagnostic of Spontaneous Bacterial Peritonitis (SBP). Increased neutrophils >250/mm³ is associated with peritonitis (bacterial, tuberculosis, pancreatic or malignancy), >1000/ mm³ is predominantly associated with bacterial and tuberculosis peritonitis Red cell count >50000/ µl seen in haemorrhagic ascites, usually due to malignancy, tuberculosis or trauma Amylase Amylase activity in ascites of non-pancreatic origin was generally about half the plasma value giving a mean ratio of / (standard deviation) (range ). Two patients with pancreatitis have been reported to have ascites/serum ratio >5 Page 2 of 6

3 Triglyceride Chylous ascites is defined on the basis of an ascitic fluid triglyceride concentration greater than 2.25 mmol/l and which is also greater than the corresponding serum concentration Bilirubin An ascitic fluid value >103 µmol/l and which is also greater than the serum value is consistent with an intrahepatic or gallbladder fistula or upper gut perforation Creatinine An ascitic fluid creatinine level greater than the serum creatinine level indicates urine leak Pleural fluid Total protein total protein <25g/L suggestive of transudate total protein >35g/L suggestive of exudate Lights criteria for an exudate -ratio of fluid protein to serum protein is >0.5 -pleural fluid LDH divided by serum LDH >0.6 -pleural fluid LDH more than two-thirds the upper limits of normal serum LDH Please note: inclusion of LDH in lights criteria does not significantly improve the discrimination compared to protein alone Differential cell counts Haematocrit If the haematocrit on the pleural fluid is less than 1%, the blood in the pleural fluid is not significant. A haematocrit of more than half the peripheral haematocrit confirms haemothorax ph Normal ph is 7.6. a ph < 7.3 is associated with inflammatory states. The British Thoracic Society agree that ph values less than 7.20 are a critical value with a parapneumonic infection and will require immediate drainage via chest tube insertion Glucose Rheumatoid arthritis is unlikely to be the cause of an effusion if the glucose level in the fluid is above 1.6 mmol/l Amylase Pleural fluid amylase levels are elevated if they are higher Page 3 of 6

4 than the upper limits of normal for serum or the pleural fluid/serum ratio is >1.0. This suggests acute pancreatitis, pancreatic pseudocyst, rupture of the oesophagus, ruptured ectopic pregnancy, or pleural malignancy (especially adenocarcinoma). Approximately 10% of malignant effusions have raised pleural amylase levels Triglyceride A true chylothorax will usually have a high triglyceride level, usually >1.24 mmol/l (110 mg/ dl), and can usually be excluded if the triglyceride level is <0.56 mmol/l (50 mg/dl). The biochemistry laboratory should be asked to look for the presence of chylomicrons between these values. In a pseudochylothorax the cholesterol level is >5.18 mmol/l (200 mg/dl), chylomicrons are not found, and cholesterol crystals are often seen at microscopy Creatinine Urointhorax diagnosis can be confirmed if pleural fluid creatinine level is greater than the serum creatinine level Clinical decision values For in depth guidance please refer to the biochemistry of body fluids, Association of Clinical Biochemists 2009 The British Thoracic Society agree that ph values less than 7.20 are a critical value with a parapneumonic infection and will require immediate drainage via chest tube insertion The presence of organisms identified by Gram stain and/or culture from a non-purulent pleural fluid sample indicates that pleural infection is established and should lead to prompt chest tube drainage. However some frankly purulent or culture-positive parapneumonic effusions due to Streptococcus pneumonia may resolve with antibiotics alone. Decisions regarding pleural drainage should be made on an individual basis. Also note that failures in aseptic technique could lead to contaminants from skin flora being grown Factors affecting performance The correct preservative must be used for each sample Air contamination will affect the ph in same way as for blood gas analysis It has been reported that diuretic therapy result in increased pleural protein Posture, prolonged tourniquet application, acute phase response and diuretic can affect albumin concentration and the SAAG. Raised amylase also found in bowel perforation, ischemia or mesenteric thrombosis Page 4 of 6

5 The weakness of Lights criteria is that they occasionally identify an effusion in a patient with left ventricular failure on diuretics as an exudate. In this circumstance, clinical judgement should be used Turnaround times: Patient preparation Instructions for patient collected sample Sample transportation Special handling needs Patient consent required Specific rejection criteria Additional information No specific requirements Not applicable Received in the laboratory preferably within 30 minutes of collection No specific requirements Implied consent Generic rejection applies Please note it is important to appreciate that with the exception of fluid ph the assays currently used have not been optimized and validated for use in fluid other than serum/plasma and may give inaccurate results References The biochemistry of body fluids ACBI 2009 Biochemical analysis of ascitic (peritoneal) fluid: what should we measure? A C Tarn1 and R Lapworth Ann Clin Biochem 2010; 47: DOI Biochemical analysis of pleural fluid: what should we measure? Anne C Tarn and Ruth Lapworth Ann Clin Biochem 2001; 38: 311±322 Letters to the editor, BTS guidelines for investigation of unilateral pleural effusion in adults response. Anne C Tarn and Ruth Lapworth. Thorax 2004;59: Comparison of Pleural Fluid ph Values Obtained Using Blood Gas Machine, ph Meter, and ph Indicator Strip* Dong-sheng Cheng, CHEST 1998; 114: Clinically Important Factors Influencing the Diagnostic Measurement of Pleural Fluid ph and Glucose Najib M. Rahman1, AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE VOL Treatment of Congestive Heart Failure*Its Effect on Pleural Fluid Chemistry Simon C. Chakko et al Chest 1989; 95: ) Page 5 of 6

6 Guidelines on the management of ascites in cirrhosis. K P Moore, G P Aithal Gut 2006;55(Suppl VI) BTS guidelines for the investigation of a unilateral pleuraleffusion in adults N A Maskell, R J A Butland, on behalf of the British Thoracic Society Pleural Disease Group, a subgroup of the British Thoracic Society Standards of Care Committee. Thorax 2003;58(Suppl II):ii8-ii17 Page 6 of 6