Must Know Values & Formulas - Exam 1

Chemistry Reference Ranges: pt 1

• Sodium: 136-145 mmol/L

• Potassium: 3.5-5.0 mmol/L

• Chloride: 98-107 mmol/L

• Total CO2: 22-33 mmol/L

• Creatinine: 0.8-1.2 mg/dL

• Blood Urea Nitrogen (BUN): 6-20 mg/dL

• Glucose (fasting): 74-100 mg/dL

• Hemoglobin: < 5.7%

• Haptoglobin: 30-200 mg/dL

Wavelength Values

Wavelength + Color

• < 380 = UV, not visible

• 380-440 = Violet

• 440-500 = Blue

• 500-580 = Green

• 580-600 = Yellow

• 600-620 = Orange

• 620-750 = Red

• 750-2000 = IR, not visible

Visible Region Color Wheel

• Chromagen absorbs wavelengths and transmits the remaining wavelengths.

• Beer’s Law: concentration → absorbance.

• absorbed wavelength used to measure concentration is complementary to the transmitted wavelength.

• Relationships:

  • red ⇌ green

  • blue ⇌ orange

  • yellow ⇌ purple.

Complementary Colors

• red ⇌ green

• blue ⇌ orange

• yellow ⇌ purple

Bichromatic Analysis Calculations

Corrected Absorbance=Aλ1​​−Aλ2​​

Where:

• Aλ1​​ is the absorbance at the primary wavelength (where the analyte has maximum absorption).

• Aλ2​​ is the absorbance at the secondary wavelength (where the analyte has minimal absorption but interfering substances absorb significantly)

Beers Law

A = εbc

Beers Law Application: Standard Curve

Conc(u)/Conc(s) = Abs (u)/Abs (s)
Conc(u)= [Abs (u) * Conc(s) ] / Abs (s)

Diagnostic Criteria of Diabetes

• Fasting Plasma Glucose (FPG) ≥ 126 mg/dL

• 2-hour Plasma Glucose (OGTT) ≥ 200 mg/dL

• HbA1c ≥ 6.5%

• Random Plasma Glucose (RPG) ≥ 200 mg/dL with symptoms

• FPG + HbA1: FPG ≥126 mg/dL & HbA1c ≥6.5% on the same occasion

Fasting Plasma Glucose (FPG)

Diagnostic Threshold + Confirmation Needed?

• ≥126 mg/dL

• No if symptomatic

• Yes if asymptomatic (repeat test or another diagnostic test required

2-Hour OGTT (2h-PG)

Diagnostic Threshold + Confirmation Needed?

• ≥200 mg/dL

• No if symptomatic

• Yes if asymptomatic (repeat test or another diagnostic test required

HbA1c

Diagnostic Threshold + Confirmation Needed?

• ≥6.5 mg/dL

• No if symptomatic

• Yes if asymptomatic (repeat test or another diagnostic test required

Random Plasma Glucose (RPG)

Diagnostic Threshold + Confirmation Needed?

• ≥200 mg/dL

• No if symptomatic

• Yes if asymptomatic (repeat test or another diagnostic test required

FPG + HbA1c

Diagnostic Threshold + Confirmation Needed?

• FPG ≥126 mg/dL & HbA1c ≥6.5% on the same occasion

• No (diabetes confirmed even in asymptomatic patients).

• If discordant, repeat abnormal test.

Diagnostic Criteria of Diabetes Explanation

1. Symptoms indicate diabetes if hyperglycemia is present

2. one test meeting the threshold is sufficient. Asymptomatic patients require a confirmatory test.

3. RPG ≥200 mg/dL is diagnostic only with symptoms.

4. If FPG ≥126 mg/dL and HbA1c ≥6.5% are both abnormal on the same occasion = diabetes confirmed

Diagnostic Criteria of Diabetes: Symptoms Matter

If a patient has symptoms of hyperglycemia (e.g., excessive thirst, frequent urination, weight loss), a single diagnostic test meeting the threshold confirms diabetes—no repeat test needed.

Diagnostic Criteria of Diabetes - Asymptomatic Patients Need Confirmation:

If a patient has no symptoms, a second confirmatory test (either the same test repeated on a different day or a different test) is needed.

Diagnostic Criteria of Diabetes - RPG Exception:

RPG ≥200 mg/dL is diagnostic only if symptoms are present. If asymptomatic, a second test (FPG, HbA1c, or OGTT) is required.

Diagnostic Criteria of Diabetes - Combining Tests:

If FPG ≥126 mg/dL and HbA1c ≥6.5% are both abnormal on the same occasion, diabetes is confirmed even in asymptomatic patients. If discordant, repeat the abnormal test.

Diabetes Critical Values:

• Hypoglycemia: Panic value is <50 mg/dL

• Hyperglycemia: Panic value is >500 mg/dL

Diagnostic Criteria for GDM

Diagnosis is based on glucose levels during pregnancy, including FPG ≥92 mg/dL, 1-hour OGTT ≥180 mg/dL, or 2-hour OGTT ≥153 mg/dL.

Diagnostic Criteria for DM

Diagnosis is based on glucose levels, including FPG ≥126 mg/dL, 2-hour OGTT ≥200 mg/dL, or HbA1c ≥6.5%. Urine Glucose: 180-200 mg/dL

Glucose Hexokinase Method: Important Enzymes and Substrates

1.D-glucose + ATP(Mg++) + hexokinase → glucose-6- phosphate + ADP

• EDTA anticoagulant binds Mg⁺⁺ = increased false negatives

2.glucose-6-P + NAD⁺ (or NADP⁺) + G6PD → 6-phosphogluconic acid + NADH (or  NADPH) + H⁺    

Glycated Hemoglobin (HbA1c)

• Reflects average glucose over 2-3 months

• Target < 7.0% for most adults

GOD POD method: Important Enzymes and Substrates

1. Beta-D glucose + O2 + glucose oxidase → gluconic acid + H2O2

2. H2O2 + reduced dye + peroxidase → color, oxidized dye + H2O2

Renal Threshold and Glucose

the plasma glucose concentration at which glucose begins to appear in the urine, typically around 180-200 mg/dL.

Analytical Methods for Glycosylated Hemoglobin

Glycosylated Hgb  = Total Hgb  -  Non-glycosylated Hgb

Comparison for SIADH, Diabetes Insipidus, and End-Stage Renal Disease

• SIADH → Water retention → Hyponatremia → Concentrated urine.

• DI → Water loss → Hypernatremia → Dilute urine.

• ESRD → Impaired sodium/water handling → Often dilutional hyponatremia → Urine osmolality depends on kidney function.

• Thiazide diuretics ( block sodium reabsorption) → Can cause hyponatremia that mimics SIADH → Increased urine sodium excretion → Treat hypertension

Serum Sodium

Parameter	SIADH (Excess ADH, Water Retention)	Diabetes Insipidus (DI) (Lack of ADH, Water Loss)	ESRD (Kidney Failure, Impaired Water/Sodium Handling)
Serum Sodium	Low (<135 mEq/L) (Dilutional Hyponatremia)	High (>145 mEq/L) (Water loss leads to hypernatremia)	Low (<135 mEq/L) (Mostly dilutiona

Serum Osmolality

Parameter	SIADH (Excess ADH, Water Retention)	Diabetes Insipidus (DI) (Lack of ADH, Water Loss)	ESRD (Kidney Failure, Impaired Water/Sodium Handling)
Serum Osmolality	Low (<275 mOsm/kg) (Excess water retention)	High (>295 mOsm/kg) (Concentrated due to dehydration)	Low to Normal (<275-295 mOsm/kg) (Dilutional in fluid overload

Urine Sodium

Parameter	SIADH (Excess ADH, Water Retention)	Diabetes Insipidus (DI) (Lack of ADH, Water Loss)	ESRD (Kidney Failure, Impaired Water/Sodium Handling)
Urine Sodium	High (>20-40 mEq/L) (Continued Na+ excretion despite hyponatremia)	Low (<20 mEq/L) (Due to dilute urine and water loss)	Low if oliguric (<20 mEq/L), Normal/High if residual function or diuretics

Urine Osmolality

Parameter	SIADH (Excess ADH, Water Retention)	Diabetes Insipidus (DI) (Lack of ADH, Water Loss)	ESRD (Kidney Failure, Impaired Water/Sodium Handling)
Urine Osmolality	High (>500 mOsm/kg) (Concentrated urine due to excess ADH)	Low (<300 mOsm/kg, often <200 mOsm/kg) (Dilute urine due to lack of ADH effect)	Variable: Fixed around 300 mOsm/kg in advanced ESRD due to loss of concentrating ability

Principal Plasma Electrolytes References Ranges

• Sodium: 136-145 mmol/L

• Potassium: 3.5-5.0 mmol/L

• Chloride: 98-107 mmol/L

• Total CO2: 22-33 mmol/L

Anion Gap

Alternative Formula: AG = [Na+] - [Cl- + HCO3-]

• Reference Range: 7-14 mmol/L

Osmolality Measurements

• Normal plasma osmolality: 275-300 mOsm/Kg

• Urine osmolality: 300-900 mOsm/Kg

Calculated Osmolality (simplified)

2[Na+] + [glucose]/20 + [BUN]/3

Osmolal Gap Calculation

Osmolal Gap = Measured Osmolality - Calculated Osmolality

Normal value included in calculated osmolality = 9 mOsm/K

ADH release factors

Protein Analysis Reference Range

6.5-8.3 g/dL

Acute Phase Proteins

• APP’s play a role in host defense, balance occurs due to compensation

  • Ex: Fibrinogen, CRP, AAT, C3, AAG, a2-Macroglobulin, haptoglobin and ceruloplasmin

• APP proteins increase, levels of negative APR proteins decrease

  • Ex: albumin, prealbumin and transferrin) decrease.

Positive APPs Types

• SAA

• Fibrinogen

• C-reactive protein

• Haptoglobin

• C3

• C9

• Ceruloplasmin

• a2 macroglobulin

• a1-antitrypsin

Negative APPs Types

• albumin

• transferrin

• transthyretin

• retinol-binding protein

• alpha-fetoprotein

Protein Electrophoresis: Fraction + Major Components + Clinical Significance

• Albumin + Albumin (3.5-5.0 g/dL) + Nutrition, liver function

• Alpha-1 + Acute phase reactions, liver disease

  • α1-Antitrypsin

  • α1-Acid glycoprotein

  • α1-Fetoprotein

• Alpha-2 + Nephrotic syndrome, acute inflammation

  • α2-Macroglobulin

  • Haptoglobin

  • Ceruloplasmin

• Beta + Iron status, complement activation

  • Transferrin

  • C3

  • β-Lipoprotein

• Gamma Immunoglobulins + Immune status + monoclonal gammopathies

LDL Cholesterol Calculation

Calculated using the Friedewald equation:

• LDL = Total Cholesterol - HDL - (Triglycerides/5),

  • applicable when triglycerides are <400 mg/dL.

Triglyceride Analysis

Enzymatic cascade reaction:

1. Triglycerides → Glycerol + Fatty acids (Lipase)

2. Glycerol + ATP → Glycerol-1-phosphate (Glycerol kinase)

3. Glycerol-1-phosphate → DHAP + H₂O₂ (GPO)

4. H₂O₂ + Chromogen → Colored product (Peroxidase)

NCEP Guidelines for Lipid Levels: Cholesterol, Triglycerides, Lipoprotein(s)

Parameter + Desirable Level + Reference Range

• Total Cholesterol + ≤200 mg/dL + 140-200 mg/dL

• LDL Cholesterol + ≤100 mg/dL + Varies by risk

• HDL Cholesterol + ≥60 mg/dL + >40 mg/dL

• Triglycerides + <150 mg/dL + 70-150 mg/dL

• Lipoprotein(a) + <30 mg/dL + Varies

Major Risk Factors: Atherosclerosis & Lipids - Ranges

• Age (>45 men, >55 women)

• Hypertension (>140/90 mmHg)

• Low HDL (<40 mg/dL)

• High LDL (>100 mg/dL)