Lab data interpretation in pediatrics

Common lab data interpretations in pediatrics

1. Lab data interpretation Presented by: Dr. Monther Alshahrani Saudi Board in Pediatric Medicine

2. Objectives Introduction Interpreting growth charts Interpretation of: Complete blood count Blood gas Renal function Liver function Urine analysis CSF analysis Writing a prescription

3. Introduction Laboratory  tests  help determine the presence, extent or absence of disease and monitor the effectiveness of treatment.

4. Interpreting growth charts

5. Interpreting CBC

6. Normal reference range

7. Normal reference range

8. Physiological nadir In term infants: Decrease in hemoglobin noticed at 8-12 weeks of age ( Hb 11 g/ dL ). In premature infants: Decrease in hemoglobin noticed at 6 weeks of age ( Hb 7-10 g/ dL ).

9. Approach to anemia

10. Anemia with low MCV Iron deficiency Thalassemia Sideroblastic anemia Anemia of chronic disease

11. Anemia with normal MCV

12. Anemia with normal MCV and high reticulocyte Membranopathy Enzymopathy Hemoglobinopathy Autoimmune Microangiopathic hemolytic anemia Hemorrhage

13. Anemia with high MCV Drugs Vit B12/ Folate deficiency Liver disease Hypothyrodism Post splenectomy

14. Interpreting Blood gas

15. Normal reference range

16. How to read a blood gas 1 st look at pH Normal, borderline normal or abnormal High: alkalosis, low: acidosis Then PaCO2 with pH (metabolic), against pH (respiratory) High: acidosis, low: alkalosis Then HCO3 High: alkalosis, low: acidosis

17. Example pH 7.38 PaCO2 45 HCO3 24

18. Example pH 7.37 PaCO2 54 HCO3 24

19. Example pH 7.50 PaCO2 25 HCO3 16

20. Example pH 7.25 PaCO2 26 HCO3 15

21. Anion gap Serum anion gap  =   Measured cations - Measured anions Serum anion gap  =  (Na + K) - (Cl + HCO 3 ) High anion gap > 12*

22. Causes of normal anion gap metabolic acidosis

23. Causes of high anion gap metabolic acidosis

24. Example pH 7.52 PaCO2 53 HCO3 30

25. Interpreting Renal function

26. Normal reference range

27. High urea and normal creatinine prerenal azotemia High protien diet High urea and creatinine Renal causes (impaired renal function)

28. Interpreting Liver function

29. Cholestasis or not? It is considered elevated if it is greater than 1.0 mg/ dL (17.1  micromol /L) if the total serum bilirubin is <5.0 mg/ dL  (85.5  micromol /L). Or greater than 20 percent of the total serum bilirubin if the total serum bilirubin is >5.0 mg/ dL  (85.5  micromol /L). 

30. Causes of cholestasis Extrahepatic obstruction Infection Metabolic/genetic diseases Endocrine Others

31. Interpreting Urine analysis

32. Gross visual examination Color – Yellow (light to deep amber) Clarity/turbidity – Clear or cloudy

33. Chemical examination/urine dipstick pH – 4.5-8 Specific gravity – 1.005-1.025 Glucose - ≤130 mg/d Ketones – None Nitrites – Negative Leukocyte esterase – Negative Bilirubin – Negative Urobilirubin – Small amount (0.5-1 mg/ dL ) Blood - ≤3 RBCs Protein - ≤150 mg/d

34. Microscopic examination/urine sediment RBCs - ≤2 RBCs/ hpf WBCs - ≤2-5 WBCs/ hpf Squamous epithelial cells - ≤15-20 squamous epithelial cells/ hpf Casts – 0-5 hyaline casts/ lpf Crystals – Occasionally Bacteria – None Yeast - None

35. Sensitivity and specificity of: Nitrites and Leukocyte esterase Leukocyte esterase Nitrites

36. Interpreting CSF analysis

37. Slightly high Significantly high Note: Usually TB meningitis associated with other findings in the history suggestive for it (history of travel to endemic area, contact or prolonged fever, etc.)

38. WBC in CSF Neonate Preterm less than 30 Term less than 20 Infant less than 10 Child less than 7

39. How to write a prescription

40. How to write a prescription Medication generic name Type Dose Route Interval Duration Note: calculate the dose/kg/day, never write the dose in (ml) unless you write the concentration.

41. Example You want to write acetaminophen and amoxicillin for 5 years old boy, his weight is 20 kg. Acetaminophen dose 15mg/kg/dose Amoxicillin dose 25-45mg/kg/day divided BID or TID

42. Acetaminophen 15 X 20 = 300 mg Acetaminophen syrup 300 mg PO every 6 hours PRN Amoxicillin 40 X 20 = 800 mg /day 800/2 = 400 mg /dose Amoxicillin syrup 400mg PO BID for 7 days

43. References Harriet lane handbook UpToDate

44. Thank you