A positive Schamroth test (or Schamroth's sign) indicates the absence of the diamond-shaped window (Schamroth's window) when the dorsal surfaces of the distal phalanges of corresponding fingers (typically the thumbs or index fingers) are opposed. This absence suggests possible finger clubbing.
Understanding the Schamroth Test
The Schamroth test is a clinical assessment used to evaluate for finger clubbing, a physical sign associated with various underlying medical conditions, often cardiopulmonary diseases.
How the Test Works
- The patient is asked to place the dorsal (back) surfaces of their corresponding fingernails together, typically using the thumbs or index fingers.
- Normally, a small diamond-shaped window (Schamroth's window) is visible between the nail beds at the base of the fingers. This space is created by the Lovibond angle, which is the angle between the nail plate and the proximal nail fold.
Positive vs. Negative Schamroth Test
| Result | Description | Indication |
|---|---|---|
| Negative | A diamond-shaped window (Schamroth's window) is present between the nails when they are opposed. | Absence of clubbing (generally) |
| Positive | The diamond-shaped window is absent; the nail beds are flush against each other, obliterating the space. | Possible presence of finger clubbing |
Interpretation
A positive Schamroth test is not a definitive diagnosis of any particular disease. It is a clinical sign that prompts further investigation to determine the underlying cause of the clubbing. Causes of clubbing can include lung diseases (e.g., lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis), heart diseases (e.g., cyanotic congenital heart disease, infective endocarditis), gastrointestinal diseases (e.g., inflammatory bowel disease, cirrhosis), and endocrine disorders.
It is important to note that even with a positive Schamroth test, further clinical evaluation and diagnostic testing are required to confirm the presence of clubbing and identify the underlying cause. Additionally, there can be false positives or negatives depending on technique or anatomical variations.
