Pathology and Clinical Laboratory Medicine

01Purpose and scope

• This manual supports the course Pathology and Clinical Laboratory Medicine. It describes how laboratory and pathology work is actually carried out day to day, from the moment a specimen is collected to the point a result or diagnostic report is released and acted on by a clinician. It is written for laboratory staff, pathologists in training, technologists, quality coordinators, and clinicians who need to understand what happens to their samples and why turnaround times and report wording look the way they do.
• The scope covers clinical chemistry, hematology, microbiology, transfusion medicine, molecular testing, and anatomic (surgical and cytology) pathology. Each area has its own equipment, validation requirements, and reporting conventions, so this manual focuses on the shared logic that applies across them and notes where specific areas differ. It does not teach the detailed bench technique for any single assay, and it does not replace the test-specific procedures, package inserts, or validation records that a laboratory must maintain.
• This field is regulated and high risk. Errors in specimen identification, analytic performance, or report interpretation can lead to delayed or wrong treatment. Nothing in this manual replaces qualified professional judgment, the approved procedures of your laboratory, or any authorization required for a particular test, method, or report. Where rules depend on jurisdiction, such as licensure of personnel, laboratory certification, or reporting obligations, check the current requirements with your regulator or accrediting body.

02Core principles

• The first principle is that the result is only as good as the specimen. Most preanalytic errors, including wrong patient identification, incorrect container, hemolysis, delayed transport, and improper fixation, occur before any instrument is involved. Laboratories therefore treat collection instructions, labeling rules, and rejection criteria as part of the testing process rather than as clerical details.
• The second principle is traceability. Every specimen, aliquot, slide, block, and result should be linkable to a patient, a collection event, a person who handled it, and an instrument or reagent lot. When a question arises months later about a result, the record should answer who did what, when, and with which materials. This is why laboratories insist on two patient identifiers, barcode scanning where feasible, and audit trails in the laboratory information system.
• The third principle is that analytic results need a defined meaning. A value is interpreted against a reference interval, a clinical decision threshold, or a prior result, and each of these depends on the method, the population, and the specimen type. Reference intervals are not universal. A laboratory that changes a method or instrument must verify whether its intervals still apply.
• The fourth principle is that the pathologist or laboratory director carries interpretive responsibility. Technologists verify technical performance and flag anomalies. Pathologists integrate morphology, clinical history, and other results into a diagnosis or interpretation, and they decide when a case needs further testing, a second opinion, or direct discussion with the treating team.

03Planning and preparation

• Before a test menu, instrument, or service line starts, the laboratory defines what clinical question it answers, who orders it, what specimen is needed, and what result would change management. A test that no clinician uses for decisions may still be useful for research, but it should not be offered as routine without a documented purpose. Planning also determines the required turnaround time, since a stat potassium result and a routine tissue stain have very different requirements for staffing and instrument placement.
• Validation is the central preparation task for any new or modified method. Depending on the test and regulatory setting, this includes establishing accuracy against a reference method or certified materials, precision across runs and operators, analytic measurement range, interference and carryover checks, and a reference interval or cutoff appropriate to the local population. The validation plan, acceptance criteria, raw data, and sign-off should be written before the data are collected, not reconstructed afterward.
• Staff competency is planned alongside the method. Each person performing a test needs documented training, supervised practice, and periodic reassessment. In anatomic pathology, this includes the grossing, processing, staining, and interpretation steps, and the cutting and staining quality of frozen sections deserves particular attention because it is performed under time pressure.
• Resource planning covers reagents, controls, calibrators, consumables, instrument service contracts, and information system interfaces. A common preparation gap is assuming that a new analyzer will connect to the existing laboratory information system without testing result mapping, unit conversion, and flag logic. Confirm these interfaces with test cases before go-live.

04Recommended workflow

1. 1
   : Confirm the request. Check that the order contains the patient's name, a second identifier such as date of birth or medical record number, the test requested, the collection date and time, the specimen source, and the ordering clinician. Incomplete or conflicting requests should be resolved with the ordering team before processing, and the resolution should be documented.
2. 2
   : Receive and accession the specimen. Scan or enter the specimen into the laboratory information system, print labels at the point of accession, and record the condition of the specimen on arrival. Note clotting, hemolysis, insufficient volume, leakage, or unlabeled containers. Apply the laboratory's rejection or comment policy and notify the sender when a specimen cannot be tested as received.
3. 3
   : Process and prepare the specimen for analysis. For chemistry and hematology, this means centrifugation, aliquoting, or direct loading according to the method's instructions. For surgical pathology, it means gross examination, sampling, tissue processing, embedding, sectioning, and staining. For microbiology, it means streaking or inoculating media and recording the time of setup. Each step should follow the approved procedure, and deviations should be recorded at the time they happen.
4. 4
   : Run the assay with controls. Before patient results are reported, confirm that the instrument is calibrated, that quality control materials at two levels or more fall within accepted limits, and that reagent lots are recorded. If controls fail, stop, investigate, and document the corrective action before releasing any patient results from that run. Do not repeat controls until they pass without understanding why they failed.
5. 5
   : Review and verify results. Technical reviewers check that results are plausible, that delta checks against prior results are reasonable, that flags and instrument messages are addressed, and that any result outside a predefined critical range is escalated. In microbiology and molecular testing, reviewers also confirm that the expected controls and internal standards behaved as designed.
6. 6
   : Interpret and report. For anatomic pathology and complex cases, the pathologist reviews the findings, applies the diagnostic criteria the laboratory uses, and writes a report with a clear diagnosis, relevant comments, and any recommendations for additional testing. Reports should separate what was observed from what was concluded. Critical results are communicated by phone or secure messaging to a licensed clinician, with the name of the person notified and the time recorded.
7. 7
   : Release, store, and retain. Once verified, results are released to the electronic record. Retain slides, blocks, residual specimens, and records for the periods required by your jurisdiction and accreditation standard, and follow the laboratory's disposal rules for biohazardous material.

05Quality checks, risk controls and compliance

• Quality control in the laboratory is a continuous process rather than a single check. Internal quality control involves running control materials with each batch or shift and plotting results against established ranges, often using statistical rules to detect shifts and trends before control limits are breached. External quality assessment or proficiency testing sends unknown samples from an outside provider so the laboratory can compare its results with peers. Failure in proficiency testing requires a documented investigation, not only a rerun.
• Risk controls focus on the points where errors are most likely and most harmful. Typical controls include independent verification of patient identity at collection and accessioning, barcode scanning, restricted access to result-editing functions, mandatory comments for results with known interferences, and defined critical value lists. Laboratories often run failure mode and effects analysis on high-risk processes such as blood transfusion compatibility testing, where a wrong-blood-in-tube error can be fatal.
• Compliance requirements vary by setting. In the United States, laboratories performing testing on human specimens for diagnosis or treatment fall under the Clinical Laboratory Improvement Amendments and must hold a certificate appropriate to their complexity level. Many laboratories also seek accreditation from bodies such as the College of American Pathologists or through ISO 15189 for medical laboratories. Other countries and regions have their own regulators and standards. Confirm current requirements with the authority that governs your site, because details change and local rules may be stricter.
• Standards from the Clinical and Laboratory Standards Institute provide widely used guidance on method evaluation, quality control, and specimen handling, and many laboratories adopt their documents as the basis for procedures. Apply them as written and document any justified deviation. Personnel licensure, specimen transport rules, and biosafety requirements are also jurisdiction specific and should be verified locally.

06Collaboration and documentation

• Laboratory work depends on close contact with clinicians, nursing staff, phlebotomy teams, and other departments. Useful collaboration includes agreeing on collection instructions, clarifying when a test is appropriate, explaining unexpected results in plain language, and receiving feedback on how reports are used. A pathologist who is available for consultation during case conferences often prevents misunderstandings that would otherwise surface as complaints weeks later.
• Documentation serves two purposes: it allows another trained person to reproduce the work, and it provides evidence during audits or investigations. Standard operating procedures should be controlled documents with version numbers, approval dates recorded in the document system, and a defined review cycle. Logs for temperatures, instrument maintenance, quality control, and staff training should be complete, legible, and reviewed by a supervisor.
• Corrected reports need explicit handling. When a released result is found to be wrong, the laboratory issues a corrected report that clearly states what changed and why, retains the original in the record, and notifies the clinician who received the first version. Amending a report silently is one of the most serious professional failures in this field.
• Communication with patients usually runs through the treating clinician. Laboratories should not give patients diagnostic interpretations directly unless their jurisdiction and policy explicitly allow it, and they should route patient questions through the appropriate channel.

07Measures and continuous improvement

• Laboratories track indicators that reflect both efficiency and safety. Common measures include turnaround time from receipt to release, percentage of specimens rejected for preanalytic reasons, rate of unlabeled or mislabeled specimens, number of QC failures per method, proficiency testing performance, rate of corrected reports, and time to complete critical result notification. Targets should be set locally, based on clinical need and past performance, rather than copied from another laboratory without context.
• Indicators are only useful if someone reviews them and acts. Many laboratories hold a monthly quality meeting where trends are examined, root causes are discussed, and actions are assigned with owners and due dates. Incident reports, including near misses, feed into this process. A useful habit is to ask what would have happened if the error had not been caught, then design a control that targets that path.
• Improvement projects need clear boundaries. Changing a collection tube type, moving a test to a different analyzer, or altering reflex testing rules each affects several downstream processes. Evaluate the change against a baseline, run it in parallel where possible, and define a rollback plan. Limits of improvement should also be recognized: some errors cannot be eliminated and must be managed through detection and clear communication.
• Trade-offs are common. Faster turnaround may reduce the time available for technical review. Stronger rejection policies reduce analytic error but may increase recollection burden on patients and clinics. Decisions of this kind belong to the laboratory director or quality committee, with clinical input, and they should be recorded with the reasons.

08Common mistakes and how to prevent them

• One frequent mistake is accepting a specimen with an incomplete or mismatched label because the request is urgent. The safer practice is to stop, contact the sender, and document the call. Verbal reassurance from a colleague is not a substitute for a corrected label.
• Another mistake is running patient samples on an instrument after a control failure, on the reasoning that the last run looked fine. Prevent this with a clear rule that patient results are held until controls pass and the failure is documented, and make sure staff know who authorizes any exception.
• Pathologists sometimes issue reports that describe findings without a clear diagnosis, or that use uncertain language without explaining what would resolve the uncertainty. Prevent this with report templates that separate descriptive findings from the diagnosis, and with peer review of difficult cases before sign-out where practical.
• Laboratories also underestimate the effect of changes made outside the laboratory, such as a new collection tube supplier, a revised fasting instruction, or a new electronic order set. Prevent these problems by requiring that any upstream change be reviewed by the laboratory before it is implemented and by testing the change with representative specimens.
• Finally, documentation is often completed from memory at the end of a shift. This produces gaps and inconsistencies. Record steps, deviations, and results as they occur, even if the entry is brief.

09Practical checklist

• Confirm that each specimen has two patient identifiers, a collection time, and a matching request before processing.
• Record specimen condition on arrival and apply the rejection or comment policy without exception.
• Verify that controls are within accepted limits before releasing any patient results from the run.
• Review delta checks, instrument flags, and critical value lists before verification.
• Escalate critical results to a licensed clinician and document the name of the person notified and the time.
• Confirm that the approved procedure version is in use and that any deviation is recorded at the time it occurs.
• Keep traceability records for reagent lots, calibrators, instrument maintenance, and staff competency current.
• Issue corrected reports with a clear statement of what changed, and notify the clinician who received the original.
• Review quality indicators at a regular meeting and assign actions with owners and due dates.
• Confirm current regulatory and accreditation requirements for your jurisdiction with the authoritative source.

★Learning sources

• Micro Degree: Pathology and Clinical Laboratory Medicine
• Micro Degree: Healthcare Administration Practice
• Micro Degree: Physiotherapy Assistant Operations
• Micro Degree: Cardiac Care Support