Laboratory Results and Delta Checks

Laboratory Results and Quality Control

• Delta checks are comparisons of current laboratory results with previous results from the same patient to assess accuracy and detect errors.
• Alarms and flags can indicate problems with the specimen or result, such as interfering substances, numerical values outside the analytic range, or the need for confirmation.

Assessment of Clinical Significance

• Reference intervals are also known as "normal values" or "normal ranges" and are defined as the range of values into which 95% of non-diagnosed individuals will fall.
• Confirmatory tests require high specificity to be certain of the diagnosis and are usually done by the National Reference Laboratory (NRL).

Test Performance

• Sensitivity refers to finding true positives, while specificity refers to finding true negatives.
• Positive predictive value (PPV) is the probability that a patient has the disease given a positive test result, while negative predictive value (NPV) is the probability that a patient is disease-free given a negative test result.
• Altering a test cutoff has a reciprocal effect on sensitivity and specificity, resulting in an inverse relationship between the two.

Post-Analysis

• The likelihood ratio of a test is the ratio of the probability of a test result in the disease state to the probability of the same result in the non-disease state.
• The predictive value of a test increases with disease prevalence.

Hematology

• An increased Red Cell Distribution Width (RDW) correlates with anisocytosis.
• Spherocytes indicate hemolytic anemia, while codocytes indicate thalassemia.
• Leukocyte Alkaline Phosphatase (LAP) score differentiates Leukemoid reaction from Chronic Myelogenous Leukemia.

Coagulation Studies

• Prolonged PT (prothrombin time) signifies Factor VII deficiency, while prolonged aPTT (activated partial thromboplastin time) signifies Factor XII, XI, IX, or VIII deficiency.
• Prolonged PT and aPTT signify Factor I, II, V, or X deficiency or the presence of lupus anticoagulant.

Clinical Chemistry

• Examination of urinary sodium, potassium, and osmolarity can determine the causes of hyponatremia and hypernatremia.
• Liver function tests can distinguish six different liver diseases.

Types of Anemia

• Four types of anemia: iron deficiency, anemia of chronic disease, hemolytic anemia, and hyperadrenalism.

Blood Gas Results

• Blood gas results can determine the causes of metabolic vs respiratory acidosis or alkalosis.

Parasitology and Bacteriology

• Elevation of eosinophils indicates the presence of allergy and parasitic infection.
• Presence of cysts, eggs, ova, or larvae in specimens can diagnose parasitic infections.
• A positive culture along with corresponding biochemical tests provides a better diagnosis of bacterial, fungal, and viral infections.

Urinalysis

• Presence of dysmorphic RBCs in urine indicates glomerular hematuria, while presence of RTE cells (bubble cells) indicates acute tubular necrosis.

Cardiac Biomarkers

• Elevation of Cardiac Troponin (Troponin I) in serum is diagnostic of myocardial infarction in the proper clinical context.