Maharashtra HSC Medical Lab Technology (Vocational) cheat sheet

Standard precautions apply to every blood and body-fluid sample regardless of diagnosis; hand hygiene is the single most effective control measure.

Biomedical waste colour code (India): yellow - anatomical, soiled and expired pharmaceutical waste; red - contaminated recyclable plastics; white translucent - sharps in puncture-proof containers; blue - glassware and metallic implants.

Sodium hypochlorite is used at 1% (10,000 ppm) for blood spills and 0.5% for general surface disinfection; it must be prepared fresh because it loses potency on standing.

Spill procedure: absorb the fluid with paper, flood with 1% hypochlorite for 30 minutes, then wipe from the periphery towards the centre and discard as yellow-category waste.

Class II biological safety cabinets provide HEPA-filtered, partially recirculated air and protect operator, product and environment; Class I cabinets protect the operator only.

Class B fires (flammable liquids, solvents) require CO2 or dry-powder extinguishers; water is contraindicated, and electrical fires must be tackled with CO2 after isolating the power supply.

Order of donning PPE: gown first, then mask or respirator, then eye protection, and gloves last; gloves are removed first during doffing, followed by hand hygiene.

Mercury spills are managed with sulphur powder or aspiration by syringe; vacuum cleaning is prohibited because it disperses vapour.

After a needle-stick injury: wash the site with soap and water without squeezing, report immediately, and start HIV post-exposure prophylaxis ideally within 2 hours.

Adult cardiac arrest sequence: check responsiveness and breathing, call for help, then 30 chest compressions (depth 5–6 cm, rate 100–120/min) to 2 rescue breaths.

Choking in a conscious adult: up to 5 sharp back blows between the scapulae, then up to 5 abdominal thrusts (Heimlich manoeuvre), alternating until the obstruction clears.

Anaphylaxis: adrenaline 0.5 mg of 1:1000 solution intramuscularly into the anterolateral thigh, repeated every 5 minutes if required, with oxygen and IV fluid.

Shock management: lay the casualty supine, raise the legs about 30 cm, keep warm, stop obvious bleeding and withhold oral fluids.

Burns: cool with running water for about 20 minutes, remove rings and watches, do not peel adherent clothing, and never apply ice, oil or toothpaste.

Fracture immobilisation: splint must include the joints above and below the fracture, and distal pulses and sensation are checked before and after splinting.

Poisoning: never induce vomiting after ingestion of corrosives or petroleum products; activated charcoal is used only for selected poisons within one hour of ingestion.

Heat stroke: move to shade, remove excess clothing, sponge with cold water, apply ice packs to neck, axillae and groins; antipyretics such as paracetamol are ineffective.

Severe external bleeding: apply firm direct pressure with a sterile pad and pressure dressing; a tourniquet is a last resort and the time of application must be recorded.

Accuracy is closeness of a result to the true value and is governed by bias; precision is agreement among replicate results and is expressed as coefficient of variation (CV%).

Levey–Jennings chart plots daily control values against time with mean and ±1s, ±2s, ±3s limits; shifts indicate systematic error, scatter indicates random error.

Westgard multirules: 1-2s is a warning rule; 1-3s, 2-2s, R-4s, 4-1s and 10x are rejection rules and the run must not be reported.

A calibrator has an assigned value and adjusts the instrument scale; a control is analysed as an unknown specimen and only monitors performance.

Internal QC is performed daily with the patient run; external quality assessment (EQAS) is periodic, inter-laboratory and retrospective, and cannot replace daily internal QC.

Pre-analytical errors (wrong tube, haemolysis, delayed transport, incorrect fasting) account for roughly 60–70% of all laboratory errors.

ISO 15189 is the standard for medical laboratory competence used by NABL accreditation; SOPs, audit trails and documented corrective actions are mandatory.

Patient confidentiality and informed consent govern sample use; certain diseases (for example tuberculosis, cholera, HIV as per local statute) are notifiable to public health authorities.

Sensitivity is the ability to detect disease when present; specificity is the ability to exclude it when absent; predictive value depends on disease prevalence.

Anatomical position: erect, facing forward, arms by the sides with palms forward; all directional terms (medial, lateral, proximal, distal, supine, prone) refer to it.

Body planes: sagittal divides left and right, coronal divides anterior and posterior, transverse divides upper and lower.

The adult skeleton has 206 bones - 80 axial (skull, vertebral column, ribs, sternum) and 126 appendicular (limbs and girdles).

Digestive sequence: mouth → oesophagus → stomach → duodenum → jejunum → ileum → caecum → ascending, transverse, descending colon → rectum.

The right lung has three lobes and the left has two; the trachea bifurcates at the carina, at the level of the T4 vertebra.

The liver is the largest gland, lies in the right upper quadrant, receives 75% of its blood from the portal vein and secretes bile into the duodenum.

Kidneys are retroperitoneal, extending from T12 to L3, the left lying slightly higher; the nephron consists of the glomerulus plus proximal tubule, loop of Henle, distal tubule and collecting duct.

Nervous system: CNS (brain and spinal cord) and PNS, with 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Arteries carry blood away from the heart, veins carry it towards the heart, and capillaries consist of a single layer of endothelium for exchange.

Normal acid–base values: pH 7.35–7.45, pCO2 35–45 mmHg, HCO3− 22–26 mEq/L; normal electrolytes Na+ 135–145 and K+ 3.5–5.0 mEq/L.

Anaemia is defined as haemoglobin below 13 g/dL in adult males and below 12 g/dL in non-pregnant adult females.

Erythropoiesis is stimulated by erythropoietin from the kidney; the mature red cell circulates for about 120 days before splenic removal.

Necrosis types: coagulative (ischaemic organs, architecture preserved), liquefactive (brain, abscess), caseous (tuberculosis), fat (pancreatitis), fibrinoid (vasculitis).

Apoptosis is programmed, energy-dependent cell death without inflammation, in contrast to necrosis, which is pathological and provokes inflammation.

Cardinal signs of acute inflammation are redness, heat, swelling, pain and loss of function, mediated by histamine, prostaglandins and bradykinin.

Virchow triad for thrombosis: endothelial injury, abnormal blood flow (stasis or turbulence) and hypercoagulability.

Benign tumours are encapsulated and non-metastatic; malignant tumours invade and metastasise via lymphatics, blood or body cavities, and are graded by differentiation and staged by extent.

Shock types: hypovolaemic, cardiogenic, distributive (septic, anaphylactic, neurogenic) and obstructive (pulmonary embolism, cardiac tamponade).

Diabetes criteria: fasting plasma glucose ≥126 mg/dL, 2-hour post-load value ≥200 mg/dL during a 75 g OGTT, random ≥200 mg/dL with symptoms, or HbA1c ≥6.5%.

Beer–Lambert law A = ε × c × l; absorbance is proportional to concentration and path length, forming the basis of all colorimetric estimations with a reagent blank.

Bilirubin: total 0.3–1.2 mg/dL, direct (conjugated) below 0.3 mg/dL; unconjugated hyperbilirubinaemia is indirect-positive, measured by the van den Bergh reaction.

ALT is more liver-specific than AST; ALP rises in biliary obstruction and bone disease; GGT confirms a hepatobiliary source of raised ALP.

Renal profile: urea 15–45 mg/dL, creatinine 0.6–1.2 mg/dL; a raised urea-to-creatinine ratio suggests pre-renal causes.

Lipid targets: total cholesterol <200 mg/dL, LDL <100 mg/dL, HDL >40 mg/dL (men) and >50 mg/dL (women), triglycerides <150 mg/dL.

Cardiac troponin I or T is the most specific marker of myocardial infarction; CK-MB rises earlier but is less specific.

Lipase is more specific than amylase for acute pancreatitis and remains elevated longer.

Anion gap = Na+ − (Cl− + HCO3−), normally 8–16 mEq/L; it increases in ketoacidosis, lactic acidosis and renal failure.

Adult reference values: Hb 13–17 g/dL (male) and 12–15 g/dL (female); PCV approximately three times the Hb; WBC 4,000–11,000/µL; platelets 1.5–4.5 lakh/µL.

Anaemia by MCV: microcytic <80 fL (iron deficiency, thalassaemia), normocytic 80–100 fL (haemolysis, chronic disease), macrocytic >100 fL (vitamin B12 or folate deficiency).

Coagulation: PT 11–14 s (INR 0.8–1.2), aPTT 25–35 s, bleeding time 2–7 min; PT monitors warfarin and aPTT monitors heparin.

Group O negative is the universal red cell donor and group AB positive the universal recipient; group O plasma contains both anti-A and anti-B.

Red cells are stored at 2–6 °C (CPD 21 days, CPDA-1 35 days); platelets at 20–24 °C with gentle agitation for 5 days; fresh frozen plasma at −30 °C or colder.

Before transfusion, ABO and Rh grouping plus a cross-match (immediate spin and antihuman globulin phase) and antibody screening are performed.

Sickle cell disease: HbS on electrophoresis or HPLC, sickled cells on peripheral smear, positive sodium metabisulphite solubility test.

Chronic myeloid leukaemia is associated with the Philadelphia chromosome t(9;22); acute lymphoblastic leukaemia is the commonest childhood leukaemia.

ESR by Westergren is normally under 15 mm/hour in men and under 20 mm/hour in women; it is raised by anaemia, pregnancy and inflammation.

Gram stain sequence: crystal violet, Gram's iodine, decolouriser (acetone-alcohol), safranin; Gram-positive organisms retain purple, Gram-negative organisms take up pink.

Autoclaving is 121 °C at 15 psi for 15 minutes; a hot-air oven is 160 °C for 2 hours; heat-labile solutions are sterilised by membrane filtration.

MacConkey agar is selective (bile salts, crystal violet) and differential (lactose); lactose fermenters such as E. coli form pink colonies.

Lowenstein–Jensen medium is used to culture Mycobacterium tuberculosis, taking 6–8 weeks; Ziehl–Neelsen staining shows pink acid-fast bacilli on a blue background.

Kirby–Bauer disc diffusion on Mueller–Hinton agar measures zone diameters; MIC is the lowest concentration inhibiting visible growth.

P. falciparum shows multiple ring forms, appliqué/accolé forms and banana-shaped gametocytes; thick film detects parasites and thin film identifies the species.

Intestinal parasites: Entamoeba histolytica cysts have four nuclei; Giardia lamblia trophozoites are pear-shaped with two nuclei; Ascaris, hookworm and tapeworm are diagnosed by ova in stool.

Widal test detects agglutinins against Salmonella typhi O and H antigens; VDRL and TPHA are serological tests for syphilis.

Hospital infection control requires hand hygiene, segregation of waste, disinfection of work surfaces and flame sterilisation of inoculating loops before and after use.

Normal urine: volume 1–2 L/day, pH 4.6–8.0, specific gravity 1.005–1.030, protein <150 mg/day; the first morning sample is preferred for microscopy.

Dipstick pads screen for blood, protein, glucose, ketones, nitrite, leukocyte esterase, bilirubin and urobilinogen; nitrite and leukocyte esterase together suggest urinary infection.

Microscopy thresholds: >3 RBC/high-power field is haematuria, >5 WBC/high-power field is pyuria; red cell casts indicate glomerulonephritis.

Casts: hyaline (normal or dehydration), granular (tubular injury), red cell (glomerular disease), white cell (pyelonephritis), waxy (chronic renal failure).

Urine protein is screened by heat-and-acetic-acid or sulphosalicylic acid turbidity; Esbach's reagent is used for quantitation.

CSF: clear, <5 cells/µL, protein 15–45 mg/dL, glucose 50–80 mg/dL (about 60% of blood glucose); bacterial meningitis shows neutrophils, low glucose and high protein; tuberculous and viral meningitis show lymphocytes.

Pleural fluid by Light's criteria is an exudate if protein >3 g/dL, fluid-to-serum protein ratio >0.5, or fluid LDH more than two-thirds of the serum upper limit.

Ascitic fluid with a serum-ascites albumin gradient ≥1.1 g/dL indicates portal hypertension; below 1.1 g/dL suggests tuberculosis, malignancy or pancreatitis.

Semen analysis (WHO 2010) reference values: volume ≥1.5 mL, concentration ≥15 million/mL, total motility ≥40%, normal morphology ≥4%.

Tissue processing sequence: fixation → dehydration in graded alcohols → clearing in xylene → paraffin embedding → sectioning at 3–5 µm on a microtome → staining.

10% neutral buffered formalin is the routine fixative; volume should be at least ten times the tissue volume and fixation takes 24–48 hours.

Haematoxylin is a basic dye staining nuclei blue-purple (basophilic); eosin is acidic and stains cytoplasm and collagen pink (eosinophilic).

Special stains: PAS for glycogen and fungi, Ziehl–Neelsen for acid-fast bacilli, Masson trichrome for collagen, Congo red for amyloid (apple-green birefringence under polarised light), Perl's for iron.

Frozen sections are cut in a cryostat for rapid intraoperative diagnosis, such as confirming tumour-free margins.

Cytology is exfoliative (Pap smear, sputum, urine) or aspiration-based (FNAC); FNAC smears are stained with May–Grünwald Giemsa or Papanicolaou stain.

Papanicolaou stain uses Harris haematoxylin, orange G and EA; the Bethesda system reports cervical smears as ASCUS, LSIL or HSIL.

Koilocytes with perinuclear halos indicate human papillomavirus infection in cervical smears.

Malignant cytological criteria: high nuclear-to-cytoplasmic ratio, nuclear pleomorphism, irregular nuclear membrane, coarse chromatin and prominent nucleoli.

B lymphocytes mature into plasma cells secreting antibody and mediate humoral immunity; T lymphocytes (CD4 helper, CD8 cytotoxic) mediate cell-mediated immunity.

Immunoglobulin classes: IgG is most abundant and crosses the placenta; IgM is the first antibody and a pentamer; IgA is secretory; IgE mediates allergy; IgD is a B-cell receptor.

Antigen–antibody reactions used in the laboratory: agglutination (Widal, blood grouping), precipitation, complement fixation, ELISA, immunofluorescence and Western blot.

Sandwich ELISA captures antigen between two antibodies; indirect ELISA detects patient antibody using an enzyme-labelled second antibody and a chromogenic substrate.

Hypersensitivity: type I IgE-mediated immediate, type II antibody-mediated cytotoxic, type III immune-complex, type IV delayed T-cell mediated (Mantoux test).

Autoimmune markers: rheumatoid factor and anti-CCP in rheumatoid arthritis; antinuclear antibody and anti-dsDNA in systemic lupus erythematosus.

HIV screening uses ELISA or rapid tests; reactive samples are confirmed by Western blot or line immunoassay, and IgM does not cross the placenta so it indicates recent fetal or neonatal infection.

Toxoid vaccines (tetanus, diphtheria) are inactivated toxins; live attenuated vaccines require an intact cold chain and are avoided in immunocompromised patients.

Complement is activated by the classical (IgG or IgM), alternative and lectin pathways; C3 and C4 levels fall in active immune-complex disease.

Spectrophotometer/colorimeter operation: select the wavelength of maximum absorption, set 100% transmittance with the reagent blank, then read standards and unknowns.

RCF (g) = 1.118 × 10⁻⁵ × r (cm) × RPM²; relative centrifugal force, not RPM alone, defines the effective pelleting force.

Centrifuge safety: balance tubes by weight opposite each other, never exceed the rated speed, and never open the lid while the rotor is moving.

Class A volumetric glassware is borosilicate and calibrated for accuracy; TC (to contain) pipettes deliver less than the marked volume, TD (to deliver) pipettes deliver the marked volume.

Glassware cleaning: soak in detergent or chromic acid, scrub, rinse in tap water, then in distilled water and dry; residual detergent alters colorimetric readings.

A pH meter is calibrated with buffers of pH 4.0, 7.0 and 9.2 before use; electrodes are stored in potassium chloride solution, not distilled water.

Reagents are stored at 2–8 °C unless stated, protected from light, used on a first-expiry-first-out basis, and never refrozen after thawing.

Laboratory water grades: Type I for molecular work and standards, Type II for general biochemistry, Type III for glassware rinsing; quality is judged by resistivity and conductivity.

Micropipettes are checked gravimetrically, used within their stated volume range, and pipetted with a smooth plunger action to avoid aerosol formation and droplet retention.