Approach to Lab Investigations
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Transcript of 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
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…