Clinical Laboratory Tests PDF

DEPARTMENT OF CLINICAL PHARMACY AND PHARMACY PRACTICE NIGER DELTA UNIVERSITY WILBERFORCE ISLAND BAYELSA STATE PCL 413 PHARMACOTHERAPEUTICS 1: 2 Units TOPIC: CLINICAL LABORATORY TESTS...

DEPARTMENT OF CLINICAL PHARMACY AND PHARMACY PRACTICE NIGER DELTA UNIVERSITY WILBERFORCE ISLAND BAYELSA STATE PCL 413 PHARMACOTHERAPEUTICS 1: 2 Units TOPIC: CLINICAL LABORATORY TESTS By DR TIMIPRE OKE 1. INTRODUCTION TO CLINICAL LABORATORY TESTS Clinical laboratory tests are a cornerstone of modern medical practice, providing critical information that aids in the diagnosis, treatment, and management of various health conditions. These tests involve the analysis of samples taken from the body, such as blood, urine, tissues, and other bodily fluids, to detect abnormalities or changes that can indicate disease or monitor health. 1.1 The Role of Clinical Laboratory Tests in Healthcare Clinical laboratory tests serve multiple essential functions in healthcare:  Diagnostic: They help in identifying the presence of diseases or conditions. For example, a blood test can detect infections, anemia, or other hematological disorders, while a biopsy can diagnose cancer.  Monitoring: These tests are used to monitor the progression of diseases and the effectiveness of treatments. For instance, a diabetic patient may regularly check blood glucose levels to manage their condition.  Screening: Laboratory tests can screen for diseases or risk factors before symptoms appear, allowing for early intervention. A common example is the cholesterol test, which helps in assessing the risk of cardiovascular diseases.  Prognostic: They provide information on the likely course and outcome of a disease, helping in planning appropriate treatment strategies. 1.2 Historical Background The history of clinical laboratory testing dates back to ancient times when rudimentary methods were used to examine bodily fluids. However, significant advancements have been made over the centuries:  Ancient Times: Early civilizations like the Egyptians and Greeks observed changes in urine and other body fluids to diagnose diseases.  19th Century: The development of the microscope and the germ theory of disease revolutionized laboratory medicine. The work of pioneers like Louis Pasteur and Robert Koch laid the foundation for modern microbiology.  20th Century: The invention of automated analyzers and the discovery of various biochemical markers led to the expansion of laboratory tests. Blood typing, introduced by Karl Landsteiner, and the development of the complete blood count (CBC) are notable milestones.  21st Century: Modern advancements in technology, such as molecular diagnostics and high-throughput sequencing, have further enhanced the capabilities of clinical laboratory testing. 1.3 Components of a Clinical Laboratory A clinical laboratory is a highly specialized facility that performs a wide range of tests. It typically consists of several key components:  Sample Collection Area: The section where samples are collected from patients. This can include blood draws, urine collection, and other specimen gathering.  Processing Area: Here, samples are prepared for analysis. This may involve centrifugation, staining, or other preparatory techniques.  Analytical Section: The core of the laboratory, where tests are performed using various instruments and methodologies. This section is often divided into specialized areas such as hematology, microbiology, clinical chemistry, immunology, and molecular diagnostics.  Quality Control: Ensures the reliability and accuracy of test results through rigorous protocols and standards.  Data Management: Involves the recording, analysis, and reporting of test results, often using sophisticated laboratory information systems (LIS). 1.4 Advancements in Clinical Laboratory Testing Recent advancements have significantly improved the scope, accuracy, and efficiency of clinical laboratory tests:  Automation and Robotics: Automated analyzers and robotic systems have increased throughput and reduced human error in laboratories.  Point-of-Care Testing (POCT): Portable testing devices allow for rapid results at the patient's bedside or in remote locations, improving accessibility and efficiency.  Genomics and Personalized Medicine: Advances in genetic testing and sequencing have enabled personalized treatment plans based on an individual's genetic profile.  Digital Pathology: The use of digital imaging and artificial intelligence in pathology enhances diagnostic accuracy and efficiency. 1.5 Future Trends in Clinical Laboratory Testing The field of clinical laboratory testing continues to evolve with ongoing research and technological innovations. Future trends include:  Integration of Artificial Intelligence (AI): AI and machine learning algorithms are being developed to assist in the interpretation of complex data and improve diagnostic accuracy.  Telemedicine and Remote Testing: The use of telemedicine and home testing kits is expanding, allowing patients to conduct tests and receive results without visiting a healthcare facility.  Biomarker Discovery: Ongoing research aims to identify new biomarkers for early detection and better understanding of diseases.  Sustainability: Efforts are being made to develop eco-friendly laboratory practices and reduce the environmental impact of testing procedures. Clinical laboratory tests are indispensable tools in medical practice, providing essential data that informs clinical decisions. The continuous advancements in this field promise to further enhance the accuracy, efficiency, and accessibility of diagnostic testing, ultimately improving patient care and outcomes. 2. TYPES OF CLINICAL LABORATORY TESTS Clinical laboratory tests are diverse and encompass a broad range of procedures designed to analyze various bodily fluids, tissues, and other samples. These tests help diagnose illnesses, monitor health conditions, and guide treatment decisions. Below are detailed descriptions of the primary types of clinical laboratory tests.  1. Qualitative tests provide a binary result, indicating the presence or absence of a particular substance or condition. These tests are typically used to detect the presence of a specific substance or to diagnose a particular condition. Examples include pregnancy tests, drug tests, and certain infectious disease tests.  2. Quantitative tests measure the amount or concentration of a particular substance in a sample. These tests provide a numerical value that indicates the level of the substance being measured. Examples include blood glucose level tests, cholesterol level tests, and complete blood count (CBC) tests.  3. Semi-quantitative tests provide an approximate measurement of the concentration of a substance, but not a precise numerical value. These tests use a scale or range to indicate the level of the substance being measured. They are often used when an exact measurement is not necessary or when a rapid screening is required. Examples include urine protein tests, urine glucose tests, and certain diagnostic tests for infectious diseases. 2.1 Hematology Tests Hematology tests focus on the study of blood and its components, including red blood cells, white blood cells, platelets, hemoglobin, and plasma. Key hematology tests include:  Complete Blood Count (CBC): Measures the levels of different blood cells and hemoglobin. It helps diagnose conditions such as anemia, infections, and blood disorders like leukemia.  Erythrocyte Sedimentation Rate (ESR): Measures the rate at which red blood cells settle at the bottom of a test tube. It is used to detect inflammation in the body.  Coagulation Tests: Includes tests like Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT) that assess the blood's ability to clot. These tests are crucial for diagnosing bleeding disorders and monitoring anticoagulant therapy. 2.2 Clinical Chemistry Tests Clinical chemistry tests analyze the chemical composition of body fluids, primarily blood and urine. These tests provide valuable insights into metabolic functions and organ health. Key tests include:  Basic Metabolic Panel (BMP): Measures levels of glucose, calcium, sodium, potassium, bicarbonate, chloride, blood urea nitrogen (BUN), and creatinine. It helps assess kidney function, blood sugar levels, and electrolyte balance.  Liver Function Tests (LFTs): Includes tests like ALT, AST, ALP, and bilirubin to evaluate liver health and detect liver diseases such as hepatitis and cirrhosis.  Lipid Profile: Measures cholesterol levels, including total cholesterol, LDL, HDL, and triglycerides. It helps assess the risk of cardiovascular diseases.  Thyroid Function Tests: Includes TSH, T3, and T4 tests to evaluate thyroid gland function and diagnose conditions like hypothyroidism and hyperthyroidism. 2.3 Microbiology Tests Microbiology tests identify infectious agents such as bacteria, viruses, fungi, and parasites. These tests are crucial for diagnosing infections and guiding appropriate treatment. Key tests include:  Culture and Sensitivity: Involves growing microorganisms from a sample (e.g., blood, urine, sputum) to identify the causative agent and determine its antibiotic sensitivity.  Polymerase Chain Reaction (PCR): A molecular technique that amplifies DNA or RNA to detect the presence of specific pathogens. It is highly sensitive and used for diagnosing infections like COVID-19, HIV, and tuberculosis.  Rapid Antigen Tests: Detect specific antigens from pathogens like influenza and streptococcus. These tests provide quick results and are commonly used in point -of-care settings. 2.4 Immunology and Serology Tests Immunology and serology tests examine the immune system's response to infections and other conditions. These tests detect antibodies, antigens, and immune system markers. Key tests include:  Enzyme-Linked Immunosorbent Assay (ELISA): Detects antibodies or antigens  in the blood. It is used for diagnosing infections like HIV, hepatitis, and Lyme disease.  Rheumatoid Factor (RF): Detects antibodies associated with rheumatoid arthritis and other autoimmune diseases.  Antinuclear Antibody (ANA) Test: Identifies antibodies that target the body's own tissues, helping diagnose autoimmune disorders like lupus. 2.5 Molecular Diagnostics Molecular diagnostics involve analyzing genetic material (DNA and RNA) to detect genetic mutations, infections, and other conditions. These tests have revolutionized personalized medicine and targeted therapies. Key tests include:  Genetic Testing: Identifies genetic mutations associated with inherited diseases, such as BRCA1/BRCA2 for breast cancer risk and CFTR for cystic fibrosis.  Next-Generation Sequencing (NGS): A high-throughput method that sequences entire genomes or specific genetic regions, providing comprehensive genetic information for diagnosis and treatment planning.  Fluorescent In Situ Hybridization (FISH): Detects chromosomal abnormalities and gene rearrangements, commonly used in cancer diagnostics. 2.6 Pathology Tests Pathology tests involve the examination of tissues and cells under a microscope to diagnose diseases. These tests are critical for identifying cancers, infections, and inflammatory conditions. Key tests include:  Biopsy: Involves the removal of tissue samples for microscopic examination. It helps diagnose cancers, inflammatory diseases, and infections.  Cytology: Examines individual cells from body fluids or tissues, such as Pap smears for detecting cervical cancer and fine-needle aspiration for evaluating lumps and masses.  Histopathology: Studies the microscopic structure of tissues, often after surgical removal, to identify abnormalities and aid in diagnosis. 2.7 Urinalysis Urinalysis is the examination of urine to detect and measure various substances. It provides valuable information about kidney function, metabolic disorders, and urinary tract infections. Key components of urinalysis include:  Physical Examination: Observes the color, clarity, and odor of urine.  Chemical Examination: Uses dipsticks to measure substances like glucose, protein, ketones, bilirubin, and pH.  Microscopic Examination: Identifies cells, crystals, bacteria, and other elements in urine sediment. 2.8 Toxicology Tests Toxicology tests detect and measure drugs, alcohol, and other toxic substances in the body. These tests are essential for managing poisoning cases, substance abuse, and monitoring therapeutic drug levels. Key tests include:  Drug Screening: Detects the presence of illicit drugs, prescription medications, and their metabolites in urine, blood, or saliva.  Blood Alcohol Test: Measures the concentration of alcohol in the blood, commonly used in legal and medical settings.  Therapeutic Drug Monitoring (TDM): Measures drug levels in the blood to ensure safe and effective dosing of medications like anticonvulsants, antibiotics, and immunosuppressants. Clinical laboratory tests encompass a wide array of procedures, each with its unique purpose and methodology. These tests provide critical information that aids in diagnosing diseases, monitoring health conditions, and guiding treatment decisions, ultimately improving patient care and outcomes. 3. IMPORTANCE OF CLINICAL LABORATORY TESTS Clinical laboratory tests are indispensable to modern medicine, playing a pivotal role in diagnosing, managing, and preventing diseases. Their importance extends across various aspects of healthcare, impacting patient outcomes, public health, and medical research. Below are detailed explanations of the numerous ways in which clinical laboratory tests are vital: 3.1 Accurate Diagnosis One of the primary roles of clinical laboratory tests is to aid in the accurate diagnosis of diseases. By analyzing blood, urine, tissues, and other samples, these tests can:  Identify Pathogens: Detect bacteria, viruses, fungi, and parasites causing infections.  Detect Chronic Conditions: Diagnose chronic diseases such as diabetes, hypertension, and cardiovascular diseases through biomarkers like glucose, cholesterol, and blood pressure levels.  Diagnose Genetic Disorders: Identify genetic mutations and chromosomal abnormalities that lead to inherited conditions, enabling early intervention and management. 3.2 Treatment Planning and Monitoring Laboratory tests provide essential information that guides treatment decisions and monitors the effectiveness of therapies. This includes:  Personalized Medicine: Identifying specific genetic mutations and biomarkers that allow for tailored treatments, especially in cancer therapy.  Drug Monitoring: Ensuring appropriate drug dosages through therapeutic drug monitoring, preventing toxicity, and ensuring efficacy.  Monitoring Disease Progression: Regular tests track the progression of chronic diseases like diabetes (HbA1c levels) and kidney disease (creatinine and BUN levels), allowing for timely adjustments in treatment plans. 3.3 Early Detection and Prevention Early detection of diseases significantly improves patient outcomes, and laboratory tests play a crucial role in this area by:  Screening Programs: Routine screening tests like mammograms, Pap smears, and colonoscopies detect early signs of cancer and other diseases, facilitating early intervention.  Preventive Health Check-ups: Regular health check-ups that include blood tests, urinalysis, and other screenings help detect potential health issues before they become serious.   Risk Assessment: Identifying individuals at high risk for certain conditions (e.g., high cholesterol levels indicating risk for heart disease), allowing for preventive measures to be taken. 3.4 Public Health Surveillance Clinical laboratory tests are vital for public health surveillance and controlling the spread of infectious diseases. This is achieved through:  Outbreak Detection: Rapid identification of infectious agents responsible for outbreaks (e.g., COVID-19, influenza) enables timely public health responses.  Vaccination Efficacy: Monitoring the effectiveness of vaccination programs through serological testing and identifying the need for booster doses.  Antimicrobial Resistance: Tracking patterns of antimicrobial resistance helps guide public health policies and the development of new antibiotics. 3.5 Research and Development Laboratory tests are foundational to biomedical research and the development of new diagnostics, treatments, and vaccines. Their contributions include:  Clinical Trials: Laboratory tests are used to evaluate the safety and efficacy of new drugs and treatments in clinical trials.  Biomarker Discovery: Identifying new biomarkers for diseases, which can lead to the development of novel diagnostic tests and targeted therapies.  Understanding Disease Mechanisms: Research using laboratory tests helps uncover the underlying mechanisms of diseases, paving the way for innovative treatments. 3.6 Quality Control in Healthcare Laboratory tests ensure the quality and safety of healthcare practices by:  Infection Control: Regular testing of healthcare environments for pathogens helps prevent healthcare-associated infections.  Blood Bank Safety: Screening donated blood for infectious agents ensures the safety of blood transfusions.   Sterilization Verification: Testing sterilization processes in hospitals and clinics ensures that medical instruments are free from contaminants. 3.7 Legal and Forensic Applications Clinical laboratory tests have significant applications in legal and forensic contexts:  Toxicology Reports: Detecting drugs, alcohol, and toxic substances in biological samples is critical for forensic investigations and legal cases.  Paternity Testing: DNA testing establishes biological relationships, which is essential in legal disputes involving custody and inheritance.  Postmortem Analysis: Autopsies and related laboratory tests determine the cause of death, providing crucial information for legal and medical purposes. 3.8 Improving Patient Outcomes The ultimate goal of clinical laboratory tests is to improve patient outcomes by providing accurate and timely information that guides clinical decision-making. This results in:  Better Prognosis: Early and accurate diagnosis leads to timely and appropriate treatment, improving the prognosis for many conditions.  Reduced Healthcare Costs: Preventive and early-detection tests can reduce the need for more extensive and expensive treatments by catching diseases early.  Enhanced Quality of Life: Effective monitoring and management of chronic diseases enable patients to maintain a better quality of life through optimal treatment regimens. 3.9 Education and Training Clinical laboratory tests are essential educational tools for training healthcare professionals:  Medical Education: Medical students and trainees learn to interpret laboratory test results, an essential skill for clinical practice.  Continuing Education: Ongoing training for healthcare providers ensures they stay updated on the latest advancements in laboratory testing and interpretation. Clinical laboratory tests are integral to the healthcare system, providing critical information that underpins accurate diagnosis, effective treatment, early detection, and prevention of diseases. They support public health initiatives, advance medical research, and ultimately improve patient outcomes, making them indispensable in modern medicine. 4. INTERPRETATION OF TEST RESULTS The interpretation of clinical laboratory test results is a complex and nuanced process that requires a thorough understanding of both the test itself and the clinical context. Accurate interpretation is crucial as it directly influences clinical decisions, patient management, and outcomes. Here are the key aspects of interpreting test results: 4.1 Understanding Reference Ranges Reference ranges, also known as normal ranges, are the set of values established as typical for a healthy population. They are critical for determining whether a test result is within normal limits or indicative of a potential health issue. Interpretation involves:  Defining Normal: Reference ranges can vary based on age, sex, race, and other demographic factors. Understanding these variations is essential to accurate interpretation.  Contextual Factors: Considering a patient's baseline values and how they compare to the reference range. For instance, what is normal for one patient may be abnormal for another due to individual physiological differences.  Dynamic Ranges: Some test results may need to be interpreted relative to previous results to identify trends rather than relying solely on a single reference range. 4.2 Clinical Context Interpreting lab results cannot occur in isolation; they must be evaluated within the broader clinical context, which includes:  Patient History: A comprehensive understanding of the patient's medical history, including past illnesses, surgeries, medications, and family history.  Current Symptoms: Correlating test results with the patient’s current symptoms and physical examination findings.   Other Diagnostic Tests: Considering results from other diagnostic tests (e.g., imaging studies, biopsies) to form a complete clinical picture.  Differential Diagnosis: Using test results to narrow down potential diagnoses, considering which conditions are most consistent with the findings. 4.3 Variability and Precision Recognizing the inherent variability and precision of laboratory tests is vital:  Biological Variability: Natural fluctuations in biological markers can occur due to factors like circadian rhythms, diet, and stress. Knowing these variations helps avoid misinterpretation.  Analytical Variability: Variability in the testing process itself, such as differences between laboratories, assay methods, and reagent quality. Clinicians should consider potential sources of error or variation.  Precision and Accuracy: Understanding the sensitivity (true positive rate) and specificity (true negative rate) of tests ensures that results are interpreted correctly in terms of their likelihood to indicate true disease presence or absence. 4.4 Follow-Up and Repeat Testing Sometimes, interpreting a test result involves follow-up or repeat testing:  Confirmatory Tests: If an initial test result is abnormal, confirmatory testing may be needed to validate the finding. For example, a positive HIV test is typically followed by a confirmatory Western blot or PCR test.  Monitoring Trends: For chronic conditions, regular testing over time helps track disease progression or response to treatment. Trends in test results can be more informative than single values.  Interpreting Anomalies: Isolated abnormal results may need to be rechecked to rule out laboratory error or transient changes. 4.5 Integrating Multidisciplinary Insights Collaboration among healthcare professionals enhances the interpretation of lab results:  Consultation: Engaging specialists, such as endocrinologists, hematologists, or infectious disease experts, for insights on complex or ambiguous results.   Multidisciplinary Teams: Utilizing a team approach, including laboratory scientists, pathologists, and clinicians, ensures comprehensive interpretation.  Electronic Health Records (EHRs): Leveraging EHRs to integrate and analyze data from multiple sources, providing a holistic view of the patient’s health status. 4.6 Patient Communication Effective communication with patients about their test results is a critical aspect of interpretation:  Clear Explanation: Translating complex medical data into understandable information for patients, explaining what the results mean in layman’s terms.  Implications and Next Steps: Discussing the implications of the results and outlining the next steps, whether it be further testing, treatment changes, or lifestyle modifications.  Addressing Concerns: Providing reassurance and addressing any concerns or questions the patient may have, especially when dealing with abnormal or unexpected results. 4.7 Ethical and Legal Considerations Interpreting lab results also involves ethical and legal considerations:  Confidentiality: Ensuring patient data privacy and confidentiality, adhering to regulations such as HIPAA in the United States.  Informed Consent: Making sure patients understand the purpose of the tests and the implications of the results before they are conducted.  Documentation: Thoroughly documenting interpretations and clinical decisions based on test results to provide a clear medical record and rationale for future reference. 4.8 Impact on Treatment Decisions The ultimate goal of interpreting laboratory test results is to inform and optimize treatment decisions:  Therapeutic Adjustments: Adjusting treatment plans based on test results, such as modifying medication dosages or adding new therapies.   Patient Management: Deciding on further diagnostic evaluations, referrals to specialists, or changes in monitoring frequency.  Outcome Prediction: Using test results to predict patient outcomes and prognosis, helping guide long-term care planning. The interpretation of clinical laboratory test results is a multifaceted process that requires a deep understanding of medical principles, patient context, and laboratory science. Accurate and thoughtful interpretation is essential for effective patient care, guiding diagnosis, treatment, and ongoing management to improve health outcomes. 5. COMMON CLINICAL LABORATORY TESTS AND THEIR USES Clinical laboratory tests are essential tools in the diagnosis and management of a wide array of medical conditions. Each test provides specific information about the body's functioning and can indicate various states of health or disease. Below, we detail some of the most common clinical laboratory tests, their uses, and the values that help in diagnosing conditions, including their normal ranges. 5.1 Complete Blood Count (CBC) The CBC is a broad screening test to check for such disorders as anemia, infection, and many other diseases. White Blood Cell (WBC) Count:  Normal range: 4,000-11,000 cells/µL  High levels (Leukocytosis): >11,000 cells/µL (may indicate infection, inflammation, leukemia)  Low levels (Leukopenia): 6.1 million cells/µL (men); >5.4 million cells/µL (women) (may indicate heart disease, dehydration)  Low levels (Anemia): 15.1 g/dL (women) (may indicate polycythemia, lung disease)  Low levels: 44.3% (women) (may indicate dehydration, polycythemia)  Low levels: 56 U/L (may indicate liver damage due to hepatitis, medications, or other liver diseases) Aspartate Aminotransferase (AST):  Normal range: 10-40 U/L  High levels: >40 U/L (may indicate liver damage, heart attack, or muscle injury) Alkaline Phosphatase (ALP):  Normal range: 44-147 U/L  High levels: >147 U/L (may indicate liver disease, bile duct obstruction, or bone disorders) Gamma-Glutamyl Transferase (GGT):  Normal range: 9-48 U/L  High levels: >48 U/L (may indicate liver disease, bile duct problems, or chronic alcohol use) Total Bilirubin:  Normal range: 0.1-1.2 mg/dL  High levels: >1.2 mg/dL (may indicate liver disease, bile duct obstruction, or hemolysis) Direct (Conjugated) Bilirubin:  Normal range: 0-0.3 mg/dL  High levels: >0.3 mg/dL (may indicate liver disease or bile duct obstruction) Albumin:  Normal range: 3.5-5.0 g/dL  Low levels: 13.5 seconds (may indicate clotting disorders, liver disease, or anticoagulant therapy) International Normalized Ratio (INR):  Normal range: 0.8-1.2  Therapeutic range (for patients on anticoagulants): 2.0-3.0  High levels: >3.0 (risk of bleeding)  Low levels: 40 seconds (may indicate clotting disorders, liver disease, or heparin therapy) 5.8 D-Dimer The D-dimer test helps diagnose conditions related to abnormal blood clotting, such as deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC).   Normal range: 500 ng/mL (may indicate the presence of an abnormal blood clot) 5.9 C-Reactive Protein (CRP) CRP is a marker of inflammation and is used to detect acute and chronic inflammatory conditions, including infections and autoimmune diseases.  Normal range: 10 mg/L (may indicate acute inflammation, infection, or chronic inflammatory disease) 5.10 Erythrocyte Sedimentation Rate (ESR) ESR is a non-specific test used to detect inflammation associated with infections, cancers, and autoimmune diseases.  Normal range:  Men: 0-15 mm/hr  Women: 0-20 mm/hr  High levels: >15 mm/hr (men); >20 mm/hr (women) (may indicate inflammation, infection, or autoimmune disease) 5.11 Urinalysis Urinalysis is used to detect and manage a variety of disorders, such as urinary tract infections (UTIs), kidney disease, and diabetes.  Color: Clear to light yellow  pH: 4.5-8.0  Specific Gravity: 1.005-1.030   Protein: Negative  Glucose: Negative  Ketones: Negative  Blood: Negative  Leukocyte Esterase: Negative  Nitrites: Negative  Abnormal findings:  Protein: Positive (may indicate kidney disease)  Glucose: Positive (may indicate diabetes)  Ketones: Positive (may indicate diabetic ketoacidosis)  Blood: Positive (may indicate UTI, kidney stones, or other conditions)  Leukocyte Esterase: Positive (may indicate UTI)  Nitrites: Positive (may indicate bacterial infection) 5.12 Arterial Blood Gases (ABG) ABG tests assess lung function and the body's acid-base balance, helping diagnose respiratory and metabolic disorders.  pH:  Normal range: 7.35-7.45  High levels: >7.45 (alkalosis)  Low levels: