Laboratory Procedures

Medical assistants perform a variety of laboratory procedures in the clinical setting. Understanding CLIA regulations, quality control, normal lab values, and proper specimen handling is essential for safe and accurate laboratory testing.

---

CLIA (Clinical Laboratory Improvement Amendments)

CLIA was enacted in 1988 to ensure quality laboratory testing. It classifies tests into three categories:

CLIA Requirements for Medical Offices

• Must have a CLIA certificate appropriate for the testing complexity level performed
• Certificate of Waiver (CoW) allows only waived tests — most common for physician offices
• Must follow manufacturer's instructions for all testing procedures
• Must perform and document quality control (QC) as specified
• Records must be maintained for at least 2 years

---

Quality Control (QC)

Quality control ensures laboratory test results are accurate and reliable:

Key QC Rules

• Run controls at the beginning of each day testing is performed (or per manufacturer instructions)
• Controls must fall within the acceptable range before patient samples can be run
• If controls are out of range: Do NOT run patient samples — troubleshoot, repeat controls, document
• Document all QC results, including out-of-range values and corrective actions taken
• Reagent management: Check expiration dates, store properly, do not use expired reagents

---

Hematology

Complete Blood Count (CBC)

The CBC is one of the most commonly ordered blood tests:

WBC Differential

The WBC differential breaks down the types of white blood cells:

Memory aid: "Never Let Monkeys Eat Bananas" (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils — in order from most to least abundant)

---

Urinalysis

A complete urinalysis has three components:

1. Physical Examination

2. Chemical Analysis (Dipstick)

3. Microscopic Examination (Moderate Complexity)

---

Blood Chemistry

Common Blood Chemistry Values

---

Specimen Handling

Key Rules

• Label at the time of collection — never pre-label specimens
• Include: patient name, DOB, date/time of collection, collector initials, test requested
• Transport specimens to the lab promptly — most within 30-60 minutes
• Specimens requiring refrigeration: urine for culture (if delayed), some blood chemistries
• Never leave specimens in extreme temperatures (heat or direct sunlight)
• Maintain chain of custody for drug testing and forensic specimens

Microbiology Basics

Types of Microorganisms

Bacterial Classifications

Gram Stain

• Gram-positive: Stain purple/blue; thick cell wall (e.g., Staphylococcus, Streptococcus)
• Gram-negative: Stain pink/red; thin cell wall with outer membrane (e.g., E. coli, Neisseria)
• Gram stain helps guide antibiotic selection before culture results are available

Specimen Collection for Cultures

• Use sterile technique to avoid contamination
• Throat culture: Swab posterior pharynx and tonsils (not tongue or cheeks); used for Group A Strep
• Wound culture: Collect from the wound margin (not surface discharge)
• Urine culture: Clean-catch midstream specimen to reduce contamination
• Blood culture: Collected in special blood culture bottles (yellow-top tubes); drawn from two separate sites
• Label all specimens immediately with patient name, DOB, date/time, source, and collector initials
• Transport to lab promptly — delayed transport may allow overgrowth of contaminants

---

Coagulation Studies

Key Coagulation Facts

• Warfarin is monitored with PT/INR (extrinsic pathway)
• Heparin is monitored with PTT/aPTT (intrinsic pathway)
• Elevated PT/INR = increased bleeding risk; may need to reduce warfarin dose
• Light blue top tubes (sodium citrate) are used for coagulation studies and must be filled to the exact line — underfilling causes inaccurate results

Point-of-Care Testing (POCT)

Point-of-care testing refers to medical tests performed at or near the site of patient care (e.g., in the medical office) rather than in a reference laboratory. These tests provide rapid results for immediate clinical decision-making.

Common Point-of-Care Tests

Advantages of POCT

• Rapid results — enables immediate clinical decisions
• Convenience — testing at the point of care, no specimen transport
• Patient satisfaction — results before the patient leaves the office
• Cost-effective — reduced lab processing fees for simple tests

Limitations of POCT

• Less precise than reference laboratory testing
• Quality control still required (run controls per manufacturer instructions)
• Operator dependent — proper training is essential
• Confirmation needed — positive rapid tests may need laboratory confirmation (e.g., positive rapid strep confirmed with throat culture)

---

Hematology Additional Concepts

Erythrocyte Sedimentation Rate (ESR / Sed Rate)

• Measures how quickly RBCs settle in a test tube over 1 hour
• Normal: Males <15 mm/hr; Females <20 mm/hr
• Elevated: Indicates inflammation (not specific — elevated in infection, autoimmune disease, cancer, pregnancy)
• Used to monitor disease activity in conditions like rheumatoid arthritis and temporal arteritis
• Non-specific test — does not diagnose a specific condition

Blood Typing and Crossmatching

• ABO blood types: A, B, AB, O
• Rh factor: Positive (+) or negative (-)
• Universal donor: O negative (can donate to all blood types)
• Universal recipient: AB positive (can receive from all blood types)
• Rh incompatibility: Important in pregnancy — Rh-negative mother with Rh-positive fetus may develop antibodies (prevented with RhoGAM injection)

Complete Blood Count Reference Values Summary