CSF & Body Fluid Analysis
Every csf & body fluid analysis calculator on CalcEngines — unit converters, derived indices and interpretive tools, each with its formula, a worked example and the reference intervals it is judged against.
31 calculators in this section
- Ascitic Fluid Neutrophil Count CalculatorAbsolute polymorphonuclear count from the total white cell count and differential, with the correction for a blood-stained tap. 250 cells/mm³ is the threshold for spontaneous bacterial peritonitis — and it is treated on the count, not the culture.
- Bronchoalveolar Lavage Differential InterpreterA healthy non-smoker's lavage is more than 85% macrophages. Lymphocytosis, neutrophilia and eosinophilia each open a different differential — but only if the lavage was good enough to interpret, which is the commonest reason these numbers mislead. This page checks the sample first and the cells second.
- Chylous Effusion InterpreterA milky effusion is either chyle from a disrupted lymphatic or a long-standing effusion that has accumulated cholesterol, and the two have entirely different causes and management. Triglyceride and cholesterol separate them in most cases — but a quarter of pseudochylous effusions meet the chylous triglyceride criterion, and one in seven true chylothoraces fails it.
- CSF Albumin Quotient (Q-Albumin) CalculatorCalculate Q-albumin, the single best measure of blood-CSF barrier integrity, from CSF and serum albumin.
- CSF Albumin Unit ConverterConvert CSF albumin between mg/L, mg/dL, g/L, µg/mL and µmol/L — and get the unit right before it reaches the albumin quotient, where a factor of ten hides in plain sight.
- CSF Amyloid Beta 40 Unit ConverterConvert CSF Aβ40 between pg/mL, ng/L, µg/L, pmol/L and nmol/L — the denominator of the Aβ42/Aβ40 ratio, and 4.08% lighter than Aβ42, which is why the molar ratio is not the reported one.
- CSF Amyloid Beta 42 Unit ConverterConvert CSF Aβ42 between pg/mL, ng/L, µg/L, pmol/L and nmol/L — with the cut-off for each assay platform printed beside the platform, because they differ by more than half.
- CSF Aβ42/Aβ40 Ratio CalculatorDivide CSF Aβ42 by Aβ40 and read it against the FDA-authorised Lumipulse cut-offs — the Core 1 amyloid biomarker, and far less platform-dependent than either peptide alone.
- CSF Cell Count InterpreterRead a CSF white cell count, differential, glucose ratio and protein together rather than one line at a time. The four textbook columns — bacterial, viral, tuberculous, fungal — overlap more than the table suggests, and this page is built around the overlap: where the pattern decides, it says so, and where it does not, it names the test that does.
- CSF Glucose Unit ConverterConvert CSF glucose between mg/dL, mg/L, g/L and mmol/L — and see why the number means little without the plasma glucose drawn beside it.
- CSF IgG Index CalculatorCalculate the CSF IgG index to detect intrathecal immunoglobulin synthesis, correcting for blood-brain barrier permeability.
- CSF IgG Synthesis Rate Calculator (Tourtellotte)The Tourtellotte formula for daily intrathecal IgG production, in mg per 24 hours. All four inputs must be in the same units the formula was derived in — so the units are an input here rather than a footnote.
- CSF IgG Unit ConverterConvert CSF IgG between mg/L, mg/dL, g/L and µg/mL — mass units only, because polyclonal IgG has no single molar mass, and with the 26% gap between Mayo's interval and ARUP's.
- CSF Lactate InterpreterInterpret a CSF lactate against the 3.5 mmol/L (31.5 mg/dL) threshold for bacterial meningitis, in either unit — and with the two clinical situations that move the threshold rather than remove it.
- CSF Oligoclonal Band InterpreterIsoelectric focusing of paired cerebrospinal fluid and serum gives five patterns, and only two of them mean intrathecal synthesis. Without the serum track there is no answer at all — bands present in both compartments came from the blood. This page reads the pattern and says what the 2024 McDonald criteria now do with it.
- CSF Protein Unit ConverterConvert CSF total protein between mg/dL and mg/L, with reference ranges by site and age and the albuminocytological dissociation pattern.
- CSF to Serum Glucose Ratio InterpreterA CSF glucose of 3.0 mmol/L is normal against a serum of 5 and markedly low against a serum of 12, and it is the absolute figure that gets reported and acted on. This page reads the ratio instead, in either unit, and asks the two questions the ratio depends on: were the samples actually paired, and was the patient hyperglycaemic when they were taken?
- CSF Xanthochromia Net Bilirubin CalculatorNet bilirubin absorbance from a CSF spectrophotometric scan, against the UK national threshold of 0.007 AU. The sample must be protected from light and taken at least 12 hours after headache onset, or the result cannot exclude anything.
- Light’s Criteria Calculator (Pleural Effusion)Classify a pleural effusion as exudate or transudate from paired pleural and serum protein and LDH — meeting any one criterion is enough to call it an exudate.
- Parapneumonic Effusion Drainage Interpreter (Pleural Fluid pH)Read a pleural fluid pH against the BTS drainage thresholds, with glucose and LDH for the intermediate band. The measurement is only valid from a blood gas analyser on an anaerobic, heparinised, lidocaine-free sample.
- PD Peritonitis Effluent Cell Count InterpreterThe ISPD threshold is an effluent white cell count above 100/µL after a dwell of at least two hours, with more than half of them neutrophils — and in a rapid-cycling patient the guideline says to use the percentage rather than the count. This page applies the 2022 criteria to a specific effluent, dwell time included.
- Pleural Fluid Adenosine Deaminase InterpreterPleural adenosine deaminase is a good test for excluding tuberculous pleural effusion and a much weaker one for confirming it — and which of those two jobs it is doing depends on how much tuberculosis walks through your door. This page interprets the result against your laboratory's own cut-off and your own pre-test probability.
- Pleural Fluid LDH Unit ConverterConvert pleural fluid LDH between U/L, IU/L, µkat/L, nkat/L and µmol/s/L — and see why Light's criteria specify two-thirds of your own laboratory's upper limit rather than an absolute number.
- Pleural Fluid Protein Unit ConverterConvert pleural fluid total protein between g/dL, g/L, mg/dL and mg/L — the unit Light's criteria are written in, and the unit most laboratories outside the United States report.
- Reiber CSF Immunoglobulin Quotient CalculatorReiber's hyperbolic discrimination line for IgG, IgA and IgM, with the absolute and relative intrathecal synthesis it implies. The relationship between the immunoglobulin quotient and the albumin quotient is a curve, not a straight line — which is why a linear IgG index reads “intrathecal synthesis” on a damaged blood–CSF barrier where there is none.
- Serum-Ascites Albumin Gradient (SAAG) CalculatorCalculate the serum-ascites albumin gradient, the test that has replaced the transudate/exudate split for classifying ascites.
- Spontaneous Bacterial Peritonitis InterpreterAn ascitic neutrophil count of 250 or more is spontaneous bacterial peritonitis and is treated on the count. The harder question is the one underneath it: a perforated viscus produces exactly the same count, needs an operation rather than antibiotics, and is separated from SBP by Runyon's three ascitic fluid criteria. This page does both, and names culture-negative neutrocytic ascites and bacterascites as the separate entities they are.
- Synovial Fluid Crystal InterpreterNeedle-shaped and negatively birefringent is urate; rhomboid and positively birefringent is calcium pyrophosphate. That part is straightforward. The two things that catch people out are that finding a crystal does not exclude a septic joint — the two coexist in about one in twenty crystal arthritides — and that a normal serum urate during an attack does not exclude gout.
- Synovial Fluid White Cell Count InterpreterClassify a joint aspirate as normal, non-inflammatory, inflammatory or septic — and apply the far lower threshold that a prosthetic joint needs. A count under 50,000 does not exclude septic arthritis.
- Traumatic Tap CSF Protein Correction CalculatorBlood in the sample raises the CSF protein, and the usual correction is about 1 mg/dL per 1,000 red cells per microlitre. The published factors run from 0.8 to 1.1, and the physiologically correct value for a given patient runs from 0.6 to 1.4 — so this page gives you the number and then tells you how much to trust it.
- Traumatic Tap WBC Correction CalculatorCorrect a CSF white cell count for blood contamination from a traumatic tap, using the patient's own blood counts.