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Diagnostic, Lab & Imaging Terminology

Duration: 50 min · Level: Foundational · Module: 2. Medical Terminology & Body Systems · Focus: lab, imaging, diagnostics, results, documentation

Diagnostic tests are the daily currency of a CEHRS specialist's work. Orders go out, results come back, reports get filed — and every one of those steps depends on understanding what a test measures, what a normal result looks like, and how the finding gets documented in the EHR. You do not need to interpret labs like a clinician, but you do need to recognize a critical value when it crosses your screen, know which section of a radiology report carries the diagnosis, and understand why a bedside glucose reading has to be tied to the right encounter. This lesson covers the diagnostic vocabulary that makes accurate data entry, correct coding, and meaningful quality reporting possible.

The two workhorse lab panels​

Two lab panels appear on more orders than any others, and the exam expects you to know their components. The complete blood count (CBC) evaluates the cellular side of blood: WBC (white blood cells, normal roughly 4.5–11.0 K/μL), RBC (red blood cells), hemoglobin (Hgb), hematocrit (Hct), and platelets. Abnormal CBC values frequently trigger automated clinical alerts inside the EHR, which is why correct result entry matters.

The basic metabolic panel (BMP) measures the chemistry of the blood: sodium, potassium, chloride, CO2, BUN, creatinine, glucose, and calcium. The pair to remember is BUN and creatinine — elevations in either point toward kidney dysfunction. A useful anchor: the CBC tells you about the blood cells, the BMP tells you about the body's chemistry and kidney function.

Imaging modalities and what each is for​

Imaging terminology is best learned by what each modality does best, because that is how orders and reports describe them. X-ray is the fast first look at bone and chest. CT (computed tomography) builds cross-sectional images and excels at detailed anatomy. MRI gives superior soft-tissue detail and uses no radiation. Ultrasound is real-time, radiation-free, and the standard for obstetric imaging. PET scan maps metabolic activity and is central to cancer staging.

The contrast worth memorizing for the exam is which modalities avoid radiation — MRI and ultrasound use none — and which excel at soft tissue (MRI) versus bone (X-ray, CT). A patient's clinical question usually dictates the modality, and recognizing that logic helps you spot mis-ordered or mismatched studies.

Reading a radiology report​

Every radiology report follows the same skeleton, and knowing it tells you exactly where to look. The structure is indication (why the study was ordered), technique (how it was performed), findings (what the radiologist observed), and impression (the radiologist's conclusion).

The single most important section for documentation and coding is the impression — that is where the radiologist states the diagnosis. The "findings" section may describe everything visible, but the impression distills it into the conclusion that drives the coded diagnosis. When you are abstracting a radiology report or routing it to coding, the impression is the part that carries the billable meaning. A common error is coding from the findings narrative rather than the impression; the exam may test that you know the difference.

Critical values and point-of-care testing​

Some results are so dangerously abnormal that they cannot wait for routine reporting — these are critical values, and they require immediate notification of the ordering clinician. CEHRS staff may be the person who relays a critical value, so recognizing one is a patient-safety skill. The examples to know: potassium below 2.5 or above 6.5 mEq/L, and blood glucose below 40 or above 500 mg/dL. When a result like that lands, the protocol is notification, not filing.

Finally, point-of-care testing (POCT) brings the lab to the bedside — glucose meters, troponin tests, rapid flu and COVID tests, all run where the patient is rather than in a central lab. The documentation rule is non-negotiable: POCT results must be entered into the EHR and linked to the correct patient encounter. A bedside result that never makes it into the record, or that attaches to the wrong encounter, is a data-quality and safety failure. As the person ensuring results land in the right place, you are the safeguard against orphaned data.

Putting it into practice​

Build a diagnostic-test reference card and rehearse the high-stakes recall items until they are automatic.

  1. On one side, list the CBC components (WBC, RBC, Hgb, Hct, platelets) and the BMP components (sodium, potassium, chloride, CO2, BUN, creatinine, glucose, calcium). Note the WBC normal range and the BUN/creatinine-to-kidney connection.
  2. On the other side, draw the five imaging modalities and write one phrase for each (bone/chest, cross-sectional, soft tissue/no radiation, real-time OB/no radiation, metabolic/cancer staging).
  3. Write the four-part radiology report structure and circle "impression" as the section that carries the codable diagnosis.
  4. Memorize the critical-value thresholds — potassium <2.5 or >6.5 mEq/L, glucose <40 or >500 mg/dL — and write the one-line rule: critical value means immediate clinician notification, and POCT results must be linked to the right encounter. Self-test until you can reproduce all four cards from memory.

Key takeaways​

  • The CBC measures blood cells (WBC normal ~4.5–11.0 K/μL, RBC, Hgb, Hct, platelets); the BMP measures chemistry (sodium, potassium, chloride, CO2, BUN, creatinine, glucose, calcium), with BUN/creatinine elevations signaling kidney dysfunction.
  • Imaging modalities by purpose: X-ray (bone/chest), CT (cross-sectional), MRI (soft tissue, no radiation), ultrasound (real-time, no radiation, OB standard), PET (metabolic activity, cancer staging).
  • Radiology reports run indication → technique → findings → impression; the impression contains the radiologist's diagnosis and is what matters for coding.
  • Critical values require immediate clinician notification — know potassium <2.5 or >6.5 mEq/L and glucose <40 or >500 mg/dL; CEHRS staff may need to relay them.
  • Point-of-care tests (glucose, troponin, flu/COVID) must be documented in the EHR and linked to the correct patient encounter.
  • Understanding what each test measures enables accurate data entry, correct coding, and meaningful quality reporting — the core diagnostic responsibilities of the role.

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Part of Module 2: Medical Terminology & Body Systems.