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Approach to Lab Investigations

Approach to Lab Investigations. By Mazen Badawi , MBBS Demonstrator , Department of Medicine KAAU. General rules. 1- order what you need 2- need is determined by : criteria of diagnosis, or monitoring, or excluding 3- follow up what you ordered

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Approach to Lab Investigations

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  1. Approach to Lab Investigations By Mazen Badawi , MBBS Demonstrator , Department of Medicine KAAU

  2. General rules 1- order what you need 2- need is determined by : criteria of diagnosis, or monitoring, or excluding 3- follow up what you ordered 4- your patient deserves knowing all about him 5- special instructions to patient and nurses 6- order sheet problems

  3. MI • CK , AST, LDH : not specific • CK : MB heart, MM muscle , BB brain • AST : heart, liver • LDH : heart, liver, RBCs, other

  4. MI High AST Look for ALT High ALT Low ALT LIVER HEART

  5. MI • Troponin I • C  A  L • CK = 6 hr to 3 days • AST = 12 to 6 days • LDH = 24 to 12 days • Uses: Confirm Dx, Timing, Efficacy of treatment

  6. CSF • Sugar = 0.4 – 0.8 • Protein = 0.2 – 0.4 • Cells = 0 – 5 lymphocytes • Colorless

  7. CSF

  8. CSF Protein- cell dissociation : Acute guillian barre syndrome Paraplegia Cerebellar tumor Disseminated sclerosis

  9. CBC report • Platelet : 150 – 400 (x1000) • RBC : 4.5 – 5.5 (million) • WBC : 4 – 11 (x1000) • Neutrophils 40-70% (2500-7500 absolute) • Lymphocytes 20- 40% • BT = in vivo, 2-4 min, punct  dry  stops , measures = • CT = in vitro , 4- 8 min, in tube, measures =

  10. CBC • What will happen if BM disease?

  11. CBC • Normal retics 0.5 – 2 % • Increase in hemorrhage, hemolysis, treated anemia • Normoblasts is the same • What does it mean if Retics are 0 ?

  12. CBC • What is pokilocytosis? Anisocytosis? • Both are seen in megaloblastic, hemolytic anemia

  13. CBC • Number + size + shape of RBC : • Polycythemia : check WBC, PLT. Why?

  14. CBC • WBC : • Normal : check diff • High : Neut or Ly + Mono? • Low : Leucopenia *

  15. Anemia

  16. Urine report Volume = 800 – 1400 ml PH = 6 Protein = nil or trace Sugar = nil Bilirubin = nil or trace RBC = 0-5 WBC = 0-5 = Crystals = nil or + Casts = nil or hyaline Sp. Gravity = 1015 - 1025

  17. What to look for Nephrotic syndrome : proteinurea : 3 g/ 24hr Normal urinary protein = 0.150 gram Normal urinary albumin = 0.01 gram Pus cells : UTI Casts: coagulated proteins Hyaline casts = normal Granular = renal failure Epithelial cells = ATN White cell cast = pyelonephritis

  18. polyurea >1010 1005 Fixed 1010 functional DI DM Sugar +++ CRF Oligurea >1010 Fixed 1010 Functional No RBC , hyaline cast AGN RBC+++ cast ARF Ch. GN RBC+++ cast

  19. Kidney Function Tests Blood urea = dietary protein, tissue catabolism, liver funct, kidney funct Creatinine = kidney funct, muscle mass Creatinine clearance = calculated + measured Other indices

  20. Renal function • Calculated Creatinine clearance: (140 – age ) x wt X 0.85 female s. Cr • Or measure it in 24 hr!

  21. Stool Analysis • Fat, RBC, pus, mucus • Normal : Fat ++, RBC –ve, Pus +, Mucus +

  22. Stool Analysis Fat +++ + Steatorrhea 6 Grams + RBC DYSENTRY Maldigestion - Digested <75% Malabsorption Amoebic Pus ++ Mucus ++++ Bacillary Pus ++++ Mucus ++

  23. LFT • Bilirubin : direct , total • Protein : total, albumin, globulin • Enzymes: ALT, AST, ALP • Prothrombin time

  24. LFT • ALP is very high in : obstructive jaundice, bone lesions • GGT increases in CLD esp. alcoholic • Proteins : 70- 90 mg , A/G ratio 2/1, in CLD 1/1 • Most specific:

  25. High bilirubin = Jaundic Indirect More Direct more Both Hemolytic Obstructive hepatocellular • All normal except: • High indirect • High LDH High ALP • A/G ratio • Normal = ALD • - Decreased= CLD

  26. TB • Acid fast bacilli stain • Acid fast bacilli culture • PPD • PCR • Radiology

  27. HBV • HBsAg = 6 w  3 months, if persisted? • HBsAb = recovery + immunity after 3 m • HBc= in Bx only • HBc Ab = all phases.IgM in replication • HBeAg = infective + chronicity • HBeAb = low infectivity • PCR = best for replication

  28. Thank you…

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