12.1 Documentation, Lots, Slide Storage, and Personnel

12.1 Documentation, Lots, Slide Storage, and Personnel

Quick Answer: An IHC result is reportable only when the written procedure, the reagent lots, the control outcome, the instrument state, and a competent operator can be reconstructed. Log every antibody lot. Confirm a new lot of an existing assay with at least one known positive and one known negative tissue. Cut unstained slides lose antigenicity; store them cool, dry, and dark, and recut from the paraffin block for predictive work whenever the block remains.

This OpenExamPrep section is independent teaching on laboratory documentation covering published QIHC laboratory-operations topic areas: procedures, QC records, personnel competency, antibody lot logs, and slide storage. It is not an ASCP or CAP publication and does not claim Board or College approval.

Procedures are the locked method, not a binder ornament

Immunohistochemistry has many movable parts: clone, dilution, retrieval buffer and time, detection chemistry, chromogen, counterstain, control tissues, and scoring rules. The procedure (standard operating procedure, SOP) is the laboratory's statement of which combination is in clinical service. If the bench follows a tribal recipe that is not the signed SOP, the validation file no longer describes the work that produced the patient slide.

A usable IHC procedure names:

• Intended use and specimen types (FFPE in the laboratory's routine fixative, cytology preparations, decalcified bone if those are in service)
• Antibody identity: vendor, catalog, clone, host species, ready-to-use versus concentrate
• Working dilution or onboard protocol name, diluent, and storage of the working reagent
• Retrieval: device, buffer identity and pH class, temperature, time, and cool-down
• Detection system and chromogen, with blocking steps that belong to the method
• On-slide or batch controls required before release, and acceptance criteria for those controls
• Scoring or reporting handoff, especially for predictive markers
• What to do when controls fail: stop, investigate, repeat—not informal "tweaking" of titer on a patient slide
• Document control: version number, effective date, author, medical-director approval, and a retired-version archive

Change control belongs with the SOP. A handwritten note on the reagent fridge ("use 1:100 now") is a new method. Dilution, vendor (same clone), or incubation or retrieval time changes are not hallway decisions; they are the class of changes that CAP 2024 Goldsmith published practice addresses with a two-positive plus two-negative confirmation (numbers in Section 12.3). A clone change is a different assay and needs full revalidation. The documentation job in this section is to make those changes visible: who approved them, which version the autostainer actually ran, and which patient slides were stained under the old versus new recipe.

Keep only the current version at the bench. Outdated printouts are a classic source of "we have always retrieved for 40 minutes" after the validated method moved to 20. When two copies disagree, the signed current SOP wins, not the laminated sheet in a drawer.

QC records: the run did not happen if it cannot be reconstructed

Every staining run should leave a record that answers who ran it, when, on which instrument, with which protocol version, which reagent lots, which control tissues, and whether those controls met acceptance. If a pathologist later questions a faint HER2 membrane stain, you should be able to show that a low-expressor control passed on that rack, that the detection lot was in date, and that the instrument did not abort mid-cycle.

Do not report patient results from a run whose required controls failed. Document the failure, the investigation, and the repeat. A sticky note that says "redo" without lots and instrument times is not a QC record.

Retention follows laboratory policy and applicable U.S. laboratory rules (CLIA and accreditor inspection practices). The operational point for QIHC study is not a memorized year-count from a non-source blog; it is that stained slides, blocks, procedures, and QC logs must remain retrievable for the interval the laboratory's document-control policy states. Discarding last month's lot log because the drawer was full is a quality failure, not housekeeping.

Traceability runs in both directions. From a patient slide you should reach lot numbers and protocol version. From a quarantined detection kit you should reach every patient stained with that lot while it was in service. If the only identifier on the slide is a handwritten first name, the chain is already broken.

Personnel competency: the method includes the operator

A validated assay run by someone who was never taught the protocol is not the validated assay. Training and competency records show that named people may load the stainer, titrate a concentrate, select controls, and stop a run.

Competency is not a one-time hire quiz. After initial training, laboratories reassess testing personnel on a defined cycle. In U.S. high-complexity testing, a common CLIA-shaped pattern is assessment at six months after the person begins the testing, then at least annually—teach that structure, and follow the laboratory's written CLIA procedure rather than inventing a private calendar. Elements often include:

• Direct observation of test performance, including control selection and instrument loading
• Monitoring of recording and reporting (run logs actually completed, lots actually written)
• Review of QC results and, where used, proficiency-testing or internal concordance performance
• Assessment of problem-solving (what to do when the on-slide control is blank)
• Written or practical testing as the laboratory defines

The laboratory medical director (or qualified designee) decides who is authorized. A student or float who "just loads racks" still needs documented training if their work produces reportable stains. Direct performance, training, and supervision of IHC all count as IHC work on the credential-experience side; on the operations side, supervisors who release or troubleshoot runs still need competency files.

Personnel records also include safety training (formaldehyde, cryogenics, sharps—Chapter 13) and, where applicable, screening for staff who preview slides. Document competency gaps and retraining. Silently moving a person off HER2 without a file is not a corrective action.

Antibody lot logs

Primary antibodies, detection kits, retrieval buffers, and chromogens arrive as lots. A lot log typically captures:

• Reagent name, clone (for antibodies), catalog number, vendor
• Lot number and manufacturer expiration
• Date received, condition on receipt, storage location and temperature
• Date opened (in-use dating may be shorter than manufacturer expiration)
• Working dilution and date the working aliquot was made, if applicable
• Initials of the person who received or opened the bottle
• Link to the lot-verification slides

CAP 2024 Goldsmith published practice for a new antibody lot of an existing validated assay is confirmation with at least one known positive and one known negative tissue before clinical use; a single control tissue that contains both positive and negative cells can serve. That 1-plus-1 check is not a clone change and is not a full revalidation. It is also not optional because the bottle "looks the same."

Do not pour a new lot into an old bottle. Do not top up a working vial with a different lot. If two lots must overlap during a transition, label them as distinct reagents and complete the confirmation before patients are stained with the new lot. Detection-kit lots deserve the same discipline: a polymer lot change can shift background and sensitivity as surely as a primary lot change.

When a control pattern shifts the same week a lot changed, the lot log is the first document Section 12.4 will ask you to open. If the log does not exist, you cannot separate a lot problem from an instrument problem, and you will burn tissue repeating blindly.

Slide storage and antigenicity

Paraffin blocks, stored cool and dry, are the laboratory's antigen archive. Cut unstained slides are not equivalent. Once a section is on glass, the exposed tissue oxidizes, dries, and loses immunoreactivity at a rate that depends on the epitope, section thickness, storage temperature, humidity, and light. Nuclear hormone receptors and some membrane predictive markers are notorious for fading on stored cut slides. A gorgeous H&E from a two-year-old unstained spare does not prove that ER, PR, HER2, or PD-L1 will still label.

Practical storage rules:

• Prefer a fresh recut from the block for predictive markers and for any case sitting near a scoring cutoff.
• If cut slides must be stored, keep them cool, dry, and protected from light. Some laboratories use a desiccator, a dedicated refrigerator, or a thin paraffin coat. Follow the laboratory's validated storage, not a windowsill slide box.
• Label the cut date. A drawer of undated extras is not a validated archive.
• ASCO/CAP breast ER, PR, and HER2 handling statements recommend against using unstained sections stored longer than about six weeks for those assays. Teach that as breast-biomarker handling guidance IHC staff must know, not as an ASCP outline quotation. Other markers may fade faster or slower; the laboratory's procedure states the limit.
• Do not bake extra unstained slides at high temperature for days as a "storage method"; excess heat can harm epitopes.
• Charged slides still lose antigen. Adhesive prevents lift-off during retrieval; it does not stop oxidation on the glass.

Stained slides are retained as part of the medical record according to policy. They are not a substitute for keeping the block. If a restain is needed years later, the block—or a carefully stored, in-date unstained section—is the specimen, not a faded spare from a forgotten drawer.

The documentation chain

Think of the IHC file as a chain: procedure version → reagent lots → instrument and operator → control tissues and results → stored slides and blocks. Break any link and you cannot defend the result, you cannot investigate a shift, and you cannot show that yesterday's HER2 was the method you validated. Documentation is how quality control becomes reconstructable rather than anecdotal.