UNO Key Concepts in Diagnostic Testing and Laboratory Analysis

What is diagnostic sensitivity?

The ability of a test to detect a given disease or condition.

What is diagnostic specificity?

The ability of a test to correctly identify the absence of a given disease or condition.

What does positive predictive value indicate?

The chance of an individual having a given disease or condition if the test is abnormal.

What does negative predictive value indicate?

The chance an individual does not have a given disease or condition if the test is within the reference interval.

What environmental factor increases draw volume in evacuated blood collection tubes?

Low ambient temperature.

What environmental factor decreases draw volume in evacuated blood collection tubes?

High ambient temperature and high altitude.

What effect does very low humidity have on evacuated blood collection tubes?

It could hasten the escape of water vapor from a tube containing a wet additive, potentially compromising clinical results.

What is CTAD in relation to evacuated blood collection tubes?

A special additive mixture for coagulation testing sensitive to light, found only in glass evacuated tubes.

What is the reference range for sodium in plasma/serum?

136 to 145 mmol/L.

What is the reference range for potassium in serum?

3.5 to 5.1 mmol/L.

What are the critical values for serum potassium?

<2.5 mEq/L and >6.5 mEq/L.

What are the critical values for serum sodium?

<120 mEq/L and >160 mEq/L.

What causes hypernatremia due to excess water loss?

Diabetes insipidus, renal tubular disorder, and prolonged diarrhea.

What causes hypernatremia due to decreased water intake?

Older persons and infants.

What causes hyponatremia due to increased sodium loss?

Hypoadrenalism, potassium deficiency, and diuretic use.

What causes hyponatremia due to increased water retention?

Excess water intake, SIADH, and pseudohyponatremia.

What are the causes of hyperkalemia related to decreased renal excretion?

Acute or chronic renal failure, hypoaldosteronism, and diuretics.

What are the causes of hyperkalemia due to cellular shift?

Acidosis, muscle/cellular injury, chemotherapy, leukemia, and hemolysis.

What are the gastrointestinal losses that can lead to hypokalemia?

Vomiting, diarrhea, gastric suction, intestinal tumor, and malabsorption.

What renal losses can lead to hypokalemia?

Diuretics, mineralocorticoids, nephritis, renal tubular acidosis, hyperaldosteronism, and Cushing's syndrome.

What is the electrophoretic pattern associated with hypoalbuminemia?

Low spike for albumin.

What is the electrophoretic pattern associated with chronic liver disease?

Diffuse but large elevation of gamma-globulins.

What is indicated by a diffuse but small elevation of y-globulins?

It suggests a non-specific increase in immunoglobulins, often seen in chronic inflammatory conditions.

What characterizes dysproteinemia monoclonal immunoglobulin?

It is characterized by a sharply elevated spike in y-globulins, occasionally accompanied by elevated β-globulins.

What does hypogammaglobulinemia indicate on a serum protein electrophoresis?

It presents as a flat curve where y-globulin should be.

What are the protein changes seen in nephrotic syndrome?

Nephrotic syndrome shows a low albumin spike and very high β-globulins, with increased α2- and β-globulins and decreased y-globulins.

What is the protein pattern in protein-losing enteropathy?

It shows a low albumin spike with moderate elevation of α2-globulins.

What is the characteristic finding in alpha1-antitrypsin deficiency on serum protein electrophoresis?

It shows a flat curve where α1-globulin should be.

What are the main functions of the kidneys related to synthesis?

The kidneys synthesize erythropoietin, renin, and prostaglandins.

What metabolic functions do the kidneys perform?

They inactivate aldosterone, glucagons, insulin, activate vitamin D, and form creatine.

What substances do the kidneys excrete?

The kidneys excrete ammonia, urea, uric acid, several minerals, and toxic substances.

What proteins does the liver synthesize?

The liver synthesizes albumin, cholinesterase, coagulation proteins, cholesterol, bile salts, and glycogen.

What metabolic processes does the liver perform?

The liver converts glucose to acetyl-CoA, performs gluconeogenesis, amino acid conversions, and fatty acid metabolism.

What detoxification functions does the liver serve?

The liver detoxifies bilirubin, drugs, and ammonia.

What is the primary excretion product of the liver?

The liver excretes bile acids.

Which tests are used to determine liver viability?

AST, ALT, y-GT, bilirubin, bile acids, and coagulation tests.

How is liver transplant monitored?

It is monitored by tests of liver enzymes, cholesterol, and bilirubin.

What does an elevated anion gap indicate?

It indicates conditions like uremia, ketoacidosis, lactic acidosis, and certain poisonings.

What causes a low anion gap?

It can be caused by hypoalbuminemia or hypercalcemia.

What are the diagnostic ranges for resting plasma glucose?

Normal: <140 mg/dL; Impaired: 140-199 mg/dL; Diagnostic: ≥200 mg/dL.

What are the diagnostic ranges for fasting plasma glucose?

Normal: <100 mg/dL; Impaired: 100-125 mg/dL; Diagnostic: ≥126 mg/dL.

What are the diagnostic ranges for 2-hour OGTT?

Normal: <140 mg/dL; Impaired: 140-199 mg/dL; Diagnostic: ≥200 mg/dL.

What are the diagnostic ranges for HbA1c?

Normal: <5.7%; Impaired: 5.7-6.4%; Diagnostic: ≥6.5%.

What is the cause of respiratory acidosis?

It is caused by excess CO2 accumulation.

What is the cause of respiratory alkalosis?

It is caused by excess CO2 loss.

What causes metabolic acidosis?

It is caused by excess H+ production.

What causes metabolic alkalosis?

It is caused by excess H+ loss or excess alkali intake.

What is a random error in laboratory testing?

It is an error that varies from sample to sample, such as mislabeling or improper calibration.

What is a systematic error in laboratory testing?

It is a consistent error that affects the accuracy of results.

What airflow pattern is characteristic of BSC Class II A1?

70% of air is recirculated to the cabinet work area through HEPA, with 30% exhausted back into the room or outside.

What airflow pattern is characteristic of BSC Class II B1?

30% of air is recirculated, and 70% is exhausted.

What must exhaust cabinet air pass through before being released outside?

A dedicated duct and a HEPA filter.

What is the intake air velocity in the system similar to II, A1?

100 linear feet per minute (lfm).

What are the main categories of drugs tested in drug of abuse testing?

CNS stimulants, CNS depressants, hallucinogens or psychoactives, and antidepressants.

Name a CNS stimulant that is commonly tested in drug abuse testing.

Cocaine.

What is a common CNS depressant that is tested?

Barbiturates.

Which hallucinogen is often included in drug testing?

Phencyclidine (PCP).

What is the significance of serum bilirubin levels in the biliary system?

It indicates the overall capacity to transport bile.

What does a high ratio of direct to total bilirubin indicate?

Potential issues with biliary duct patency or hepatocellular metabolism.

What does fecal color and fat content indicate in the biliary system?

Patency of biliary ducts.

What does urine urobilinogen indicate regarding bilirubin?

It indicates the quantity of bilirubin processed and patency of biliary ducts.

What does serum alkaline phosphatase (ALP) indicate?

Abnormality of bile duct epithelium.

What does a low blood urea level suggest?

A rough estimate of lost detoxifying capacity.

What does blood ammonia level indicate?

Hepatocellular detoxifying reactions and integrity of portal circulation.

What is the significance of alpha-fetoprotein in liver function tests?

It indicates hepatocellular multiplication, which may suggest tumors or regeneration.

What is a common error that requires recollection of a specimen?

Visible hemolysis.

What does prolonged tourniquet application affect in blood tests?

It elevates the concentration of von Willebrand factor and factor VIII, falsely decreasing fibrinolytic parameters.

What is the effect of lipemia or icterus on optical instruments?

They may not measure clots accurately in cloudy or highly colored specimens.

What is the role of serum albumin level in hepatocellular function?

It indicates the capacity to synthesize protein.

What does serum aminotransferase levels indicate?

Hepatocellular damage and necrosis.

What is the purpose of testing for hepatitis A and B antigens and antibodies?

To diagnose viral hepatitis.

What does the presence of a clot in a specimen indicate?

The specimen must be recollected.

What is the significance of serum iron and ferritin levels?

High levels indicate hemochromatosis.

What does the presence of benzoylecgonine in a drug test indicate?

Cocaine use.

What is a common antidepressant tested in drug abuse testing?

Tricyclic antidepressants.

What temperature range is optimal for specimen storage to avoid precipitation of von Willebrand factor multimers?

1°C to 6°C

What happens to coagulation factors V and VIII when specimens are stored above 25°C?

They deteriorate.

What is the effect of collecting blood volume less than the specified minimum on PT results?

PT is falsely prolonged; recollect specimen.

What hematocrit level requires adjustment of anticoagulant volume during blood collection?

Hematocrit ≥ 55%.

What should be done if there is a clot in the specimen?

All results are affected unpredictably; recollect specimen.

What does visible hemolysis do to PT results?

PT is falsely shortened; recollect specimen.

How should PT be measured in cases of icterus or lipemia?

Use a mechanical coagulometer.

What reagent should be used in heparin therapy to ensure accurate results?

A reagent known to be insensitive to heparin or one that includes a heparin neutralizer such as POLYBRENE.

What is the effect of lupus anticoagulant on PT results?

PT result is invalid; use chromogenic factor X assay instead.

What reflex test is performed for deficient factor fibrinogen?

Fibrinogen assay.

What are the PT, PTT, and TCT results for a deficient factor prothrombin?

PT prolonged, PTT prolonged, TCT normal.

What reflex tests are performed for deficient factor V?

Prothrombin, V, VII, and X assays.

What are the PT, PTT, and TCT results for a deficient factor VII?

PT prolonged, PTT normal, TCT normal.

What reflex tests are performed for deficient factor VIII?

VIII, IX, and XI assays.

What are the PT, PTT, and TCT results for a deficient factor IX?

PT normal, PTT prolonged, TCT normal.

What are the PT, PTT, and TCT results for a deficient factor X?

PT prolonged, PTT prolonged, TCT normal.

What are the PT, PTT, and TCT results for a deficient factor XI?

PT normal, PTT prolonged, TCT normal.

What are the PT, PTT, and TCT results for a deficient factor XIII?

PT normal, PTT normal, TCT normal.

What is the purpose of reflex testing in laboratory analysis?

To perform repeat or additional testing under operator-defined circumstances.

What is the typical dilution for a WBC count?

1:20.

What diluting fluid is used for WBC counting?

3% acetic acid, 1% hydrochloric acid, or 1% ammonium oxalate.

What should be done after charging the hemacytometer before counting cells?

Place it in a moist chamber for 10 minutes to allow cells to settle.

What is the diluting fluid used for platelet counting?

1% ammonium oxalate.

What is the objective used for platelet counting?

40x phase.

What should be done after charging the hemacytometer for platelet counting?

Place it in a moist chamber for 15 minutes to allow cells to settle.