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

LIVER HEART

MI

Troponin IC 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 – 0.8Protein = 0.2 – 0.4 Cells = 0 – 5 lymphocytesColorless

CSFApperanceCell countGlucoseProt.Gram stainAFB

Normal

Bacterial meningitis

TB

aseptic

CSF

Protein- cell dissociation :Acute guillian barre syndromeParaplegiaCerebellar tumorDisseminated sclerosis

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 =

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 *

AnemiaNormal PLT,WBC, Clotting and bleeding time

Normochromic Hypo

Retics 10-20%

G6PD, SICKLE, SPHEROCYTOSIS

Normal retics +++retics

Eosinophils

High in parasitic infection

Normal in sidroblastic anemia

Thalassemia

Anemia with Abnormal

WBC, PLT, CT, BT

All low = pancytopenia

High WBC High BT + Purpura

Normochromic= Aplastic a .

HypersplenismAleukemic leuk.

Hyperchromic=Megaloblastic

<20000 +retics

=acute blood loss

Check BT, CT

>30000 =Leukemia

Blast +++ = acute = -chroic

If low plt=TTP

HIGHCT

COAGULATION

Urine report

Volume = 800 – 1400 ml PH = 6 Protein = nil or traceSugar = nilBilirubin = nil or traceRBC = 0-5 WBC = 0-5 =Crystals = nil or +Casts = nil or hyaline Sp. Gravity = 1015 - 1025

What to look for

Nephrotic syndrome : proteinurea : 3 g/ 24hrNormal urinary protein = 0.150 gramNormal urinary albumin = 0.01 gram Pus cells : UTICasts: coagulated proteinsHyaline casts = normalGranular = renal failureEpithelial cells = ATN White cell cast = pyelonephritis

polyurea

functional DI

>1010 1005 Fixed 1010

DMSugar +++ CRF

Oligurea

AGN RBC+++

cast

FunctionalNo RBC , hyaline

cast

>1010 Fixed 1010

ARFCh. GNRBC+++

cast

Kidney Function Tests

Blood urea = dietary protein, tissue catabolism, liver funct, kidney funct

Creatinine = kidney funct, muscle massCreatinine clearance = calculated +

measuredOther 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, mucusNormal : Fat ++, RBC –ve, Pus +,

Mucus +

Stool Analysis Fat

++++

+RBCSteatorrhea

6 Grams

DYSENTRY

BacillaryPus++++

Mucus++

AmoebicPus++ Mucus++++

MalabsorptionMaldigestion

-Digested >75%

LFT

Bilirubin : direct , totalProtein : total, albumin, globulinEnzymes: ALT, AST, ALPProthrombin time

LFT

ALP is very high in : obstructive jaundice, bone lesions

GGT increases in CLD esp. alcoholicProteins : 70- 90 mg , A/G ratio 2/1, in

CLD 1/1Most specific:

High bilirubin = Jaundic

IndirectMore

Directmore

Both

Hemolytic

All normal except:-High indirect

-High LDH

Obstructive

High ALP

hepatocellular

A/G ratio-Normal = ALD

-Decreased= CLD

TB

Acid fast bacilli stainAcid fast bacilli culturePPDPCRRadiology

HBV

HBsAg = 6 w 3 months, if persisted?HBsAb = recovery + immunity after 3 mHBc= in Bx onlyHBc Ab = all phases.IgM in replicationHBeAg = infective + chronicityHBeAb = low infectivityPCR = best for replication

Thank you…