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 4- your patient deserves knowing all about him 5- special instructions to patient and nurses 6- order sheet problems

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

MI High AST Look for ALT Low ALTHigh ALT LIVERHEART

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

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

CSF AFBGram stainProt.GlucoseCell countApperance Normal Bacterial meningitis TB aseptic

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

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

CBC What will happen if BM disease?

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

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

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

CBC WBC : 1. Normal : check diff 2. High : Neut or Ly + Mono? 3. Low : Leucopenia *

Anemia Normal PLT,WBC, Clotting and bleeding time Normochromic Retics 10-20% G6PD, SICKLE, SPHEROCYTOSIS Hypo Normal retics Eosinophils High in parasitic infection Normal in sidroblastic anemia +++ retics Thalassemia

Anemia with Abnormal WBC, PLT, CT, BT All low = pancytopenia Normochromic = Aplastic a. Hypersplenism Aleukemic leuk. Hyperchromic =Megaloblastic High WBC < retics = acute blood loss Check BT, CT >30000 = Leukemia Blast +++ = acute - = chroic High BT + Purpura If low plt =TTP HIGH CT COAGULATION

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 =

What to look for Nephrotic syndrome : proteinurea : 3 g/ 24hr Normal urinary protein = 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

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

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

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

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

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

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

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

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

TB Acid fast bacilli stain Acid fast bacilli culture PPD PCR Radiology

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

Thank you…