Egyptian Board Clinical Pathology flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Anion gap formula

Anion gap equals sodium minus the sum of chloride and bicarbonate, normally 8–12 mmol/L. A raised gap indicates accumulation of unmeasured anions such as lactate, ketones, or toxins.

Corrected calcium formula

Corrected calcium in mmol/L equals measured calcium plus 0.02 times (40 minus albumin in g/L). This adjusts for albumin-bound calcium but does not replace measurement of ionised calcium.

Friedewald LDL limitation

The Friedewald equation estimates LDL as total cholesterol minus HDL minus triglycerides divided by 2.2 in mmol/L. It is invalid when triglycerides exceed about 4.5 mmol/L, so direct LDL or non-HDL cholesterol is used.

Osmolal gap

The osmolal gap is measured osmolality minus calculated osmolality (2Na plus glucose plus urea). A gap above 10 mOsm/kg suggests unmeasured osmoles such as methanol or ethylene glycol.

HbA1c interpretation limits

HbA1c reflects mean glucose over the preceding 8–12 weeks. Results are unreliable in haemoglobinopathies, recent transfusion, pregnancy, and chronic kidney disease, where alternative glycaemic markers are needed.

Troponin kinetics

Cardiac troponin rises 3–6 hours after myocardial injury and peaks at 12–24 hours. A single value cannot exclude acute coronary syndrome, so serial sampling with a 0/1-h or 0/3-h algorithm is required.

Iron deficiency versus chronic disease

Iron deficiency shows low ferritin and transferrin saturation below 20%. Anaemia of chronic disease shows low serum iron, low TIBC, and normal or high ferritin due to hepcidin-mediated iron sequestration.

ABO compatibility rules

Group O red cells are the universal red cell donor; group AB plasma is the universal plasma donor. Group O plasma contains anti-A and anti-B and must not be given to non-O recipients.

Acute haemolytic transfusion reaction

Presents with fever, chills, flank pain, haemoglobinuria, and DIC. Management is to stop the transfusion immediately, maintain venous access, support blood pressure, and send samples for DAT and repeat crossmatch.

DIC laboratory profile

Disseminated intravascular coagulation shows prolonged PT and APTT, low fibrinogen, raised D-dimer, thrombocytopenia, and schistocytes on the blood film. Treatment targets the underlying cause.

Blood component storage

Red cells are stored at 2–6 °C for up to 35–42 days. Platelets are agitated at 20–24 °C for 5–7 days. Fresh frozen plasma is frozen within 8 hours and used within 24 hours after thawing.

Warfarin versus heparin monitoring

Warfarin is monitored by INR because it reduces functional factors II, VII, IX, and X. Unfractionated heparin is monitored by APTT and low molecular weight heparin by anti-Xa activity.

Hepatitis B serology patterns

HBsAg indicates current infection. Anti-HBc IgM indicates acute infection. Anti-HBs indicates immunity after vaccination or resolved infection. Anti-HBc IgG with anti-HBs indicates past infection.

HIV diagnostic algorithm

A fourth-generation combined antigen/antibody assay is the screen. Reactive results are confirmed by Western blot or HIV-1/2 differentiation immunoassay, with HIV RNA PCR used for indeterminate or acute cases.

Syphilis serology interpretation

Non-treponemal tests (VDRL, RPR) quantify disease activity and monitor treatment. Treponemal tests (TPHA, EIA) remain positive for life and are used to confirm the diagnosis.

Dengue serology timing

NS1 antigen is detectable in the first 5 days of illness. IgM appears from about day 5. Rapidly rising IgG suggests secondary infection.

Gram stain principle

Gram-positive organisms retain the crystal violet–iodine complex because of thick peptidoglycan. Gram-negative organisms decolourise and take up the safranin counterstain, appearing pink.

ANA testing strategy

Antinuclear antibody immunofluorescence is a screening test. Positive results require confirmation with anti-dsDNA, which tracks SLE activity, and anti-extractable nuclear antigen antibodies for specific connective tissue diseases.

Complement pattern interpretation

Low C3 and C4 with normal total haemolytic complement suggests classical pathway consumption, as in SLE or cryoglobulinaemia. Low C3 with normal C4 suggests alternative pathway activation.

Hypersensitivity types

Type I is IgE-mediated mast cell degranulation. Type II is antibody-mediated cytotoxicity. Type III is immune complex deposition. Type IV is delayed T-cell-mediated hypersensitivity.

Anti-CCP versus rheumatoid factor

Anti-CCP has higher specificity than rheumatoid factor for rheumatoid arthritis. Rheumatoid factor is also positive in Sjögren syndrome, hepatitis C, and some healthy elderly individuals.

Coeliac serology

Tissue transglutaminase IgA is the preferred screen, interpreted with a total IgA level. IgA deficiency causes false negatives and requires IgG-based assays such as IgG anti-tTG or anti-endomysial antibodies.

Formalin fixation parameters

Ten percent neutral buffered formalin penetrates at roughly 1 mm per hour. Recommended fixation is 6–48 hours for small biopsies and longer for large specimens, to preserve morphology and antigenicity.

Frozen section indications

Frozen section is used for intraoperative diagnosis, margin assessment, and confirmation of lesional tissue. It is unsuitable for lymphoid or subtle lesions because freeze artefact distorts nuclear detail.

Bethesda cytology systems

The Bethesda system standardises cervical cytology (NILM, ASC-US, LSIL, HSIL, AGC, cancer) and thyroid cytology (categories I–VI). Standardised categories guide management and allow comparison between laboratories.

Immunohistochemistry lineage markers

Cytokeratin confirms epithelial lineage, vimentin mesenchymal lineage, S100 neural crest origin, and CD45 leucocyte lineage. Interpretation requires external and internal controls to exclude non-specific staining.

PCR contamination control

Separate pre- and post-amplification areas, use uracil-N-glycosylase, and include negative extraction and no-template controls. These measures prevent and detect amplicon contamination that causes false-positive results.

ACMG variant classification

Variants are classified as pathogenic, likely pathogenic, variant of uncertain significance, likely benign, or benign. Classification integrates population frequency, computational prediction, functional data, and segregation evidence.

Karyotype versus FISH

Karyotyping requires cultured dividing cells and detects balanced translocations and numerical changes. FISH detects targeted deletions, duplications, and translocations on interphase cells without culture.

Westgard multirules

The 12s rule is a warning. The 13s, 22s, R4s, 41s, and 10x rules are rejection rules indicating random or systematic error in internal quality control.

Six Sigma in the laboratory

Sigma equals total allowable error minus bias, divided by coefficient of variation. Values above 6 indicate excellent performance, while values below 3 indicate unacceptable performance requiring process improvement.