Laboratory Values Affected by Smoking
Smoking significantly affects multiple laboratory values, with elevated hemoglobin, carboxyhemoglobin, and white blood cell counts being the most consistently altered parameters. 1, 2
Hematological Parameters
Red Blood Cell Parameters
- Hemoglobin (Hb): Increased by approximately 0.3-0.7 g/dL depending on smoking intensity
- 0.5-1 pack/day: +0.3 g/dL
- 1-2 packs/day: +0.5 g/dL
2 packs/day: +0.7 g/dL 1
- Red Blood Cell (RBC) count: Significantly elevated 2
- Hematocrit: Increased 2
- Mean Corpuscular Volume (MCV): Significantly elevated 2
- Mean Corpuscular Hemoglobin Concentration (MCHC): Significantly higher 2
White Blood Cell Parameters
- White Blood Cell (WBC) count: Significantly elevated 2, 3
- This elevation can persist for at least 4 hours after exposure to cigarette smoke 3
- Shows dose-response characteristics related to smoking intensity
- Neutrophil count: Increased 4
- Lymphocyte count: Elevated 4
- Granulocyte/Lymphocyte ratio: Significantly increased after smoking exposure 5
Platelet Parameters
- Platelet count: Elevated 4
Biochemical Parameters
Blood Gas Values
- Carboxyhemoglobin (COHb):
- Non-smokers: Normal range 3-4%
- Smokers: Generally 3-5%
- Heavy smokers: Up to 10% or higher
- Rule of thumb: Each pack per day increases COHb by approximately 2.5% 1
- Special consideration: Standard pulse oximetry cannot differentiate COHb from oxyhemoglobin, potentially giving falsely normal oxygen saturation readings 6
Inflammatory and Oxidative Stress Markers
- Fibrinogen levels: Elevated, with smoking acting as an effect modifier that enhances the impact of other cardiovascular risk factors 7
- Malondialdehyde (MDA): Significantly elevated (marker of oxidative stress) 5
- Vitamin E levels: Significantly decreased after smoking exposure 5
- Total Antioxidant Capacity (TAC): Reduced 5
Clinical Implications
Diagnostic Considerations
- When interpreting hemoglobin levels, clinicians should adjust for smoking status to avoid missing true anemia 1
- COHb measurement requires specialized blood gas analysis with CO-oximetry, as standard pulse oximetry cannot detect it 6
- Elevated WBC counts in smokers may be misinterpreted as indicating infection or inflammation 3
Cardiovascular Risk Assessment
- Smoking significantly increases cardiovascular risk markers and modifies the impact of other risk factors 7
- The combination of smoking with other cardiovascular risk factors has a more than additive effect on fibrinogen levels 7
Reversibility
- Many hematological abnormalities begin to normalize rapidly after smoking cessation
- Parameters showing quick improvement include hemoglobin concentration, packed cell volume, RBC count, WBC count, neutrophil count, lymphocyte count, and platelet count 4
- This indicates that at least some smoking-related laboratory abnormalities are acute, reversible effects rather than responses to tissue damage 4
Passive Smoking Effects
- Even passive exposure to cigarette smoke can cause similar alterations in blood parameters as active smoking 3, 5
- WBC counts increase significantly in non-smokers exposed to second-hand smoke 3
- Oxidative stress markers may be even more adversely affected in passive smokers 5
Understanding these alterations is crucial for accurate laboratory interpretation and proper clinical decision-making in both active and passive smokers.