Final answer:
In cases of erythema nodosum, a Chest X-ray is frequently recommended to check for respiratory causes, and an Erythrocyte Sedimentation Rate (ESR) may be ordered to assess inflammation levels.
Step-by-step explanation:
The question pertains to additional tests that should be done in patients with erythema nodosum, a condition that manifests as red nodules typically on the legs or face, indicating inflammation in the subcutaneous fat cells of the hypodermis. Among the options given, a Chest X-ray is often recommended to check for associated respiratory conditions that could be the underlying etiologic agent causing the erythema nodosum, such as infections like tuberculosis or sarcoidosis. An Erythrocyte Sedimentation Rate (ESR) may also be indicated to measure the degree of inflammation present in the body, although it is a nonspecific test. Although a skin biopsy can confirm erythema nodosum, it is typically not the first test ordered. On the other hand, abdominal ultrasound is not usually a standard investigation for this condition unless there is a specific clinical indication to explore abdominal or pelvic causes of the