OnExam

Fingernail clubbing is a sign of several diseases, most notably of the heart and lungs. It is also known as "Hippocratic fingers" and is best assessed by looking for Schamroth's sign, also discussed below.

Associations

  • Lung cancer: LR+ = 3.9 (95% CI 1.6-9.4)
  • Inflammatory bowel disease
    • Ulcerative colitis: LR+ = 3.7 (95% CI 1.4-9.4), sensitivity = 30%, specificity = 92%
    • Crohn’s disease: LR+ = 2.8 (95% CI 1.8-4.1), sensitivity = 58%, specificity = 79%

Assessing for Clubbing

Inspection
  • Nail-fold angle
    • Profile angle: tangential angle made by nail as it exits from terminal phalanx (cuticle)
    • Angle is abnormal if it approaches 180°
  • Phalangeal depth ratio
    • Ratio of diameter of the finger at cuticle to the diameter of the finger at DIP joint
    • Ratios of > 1.0 indicate clubbing
  • Digital index
    • Obtained by summing the phalangeal depth ratio for all 10 fingers
    • An index of > 10.2 indicates clubbing
  • Schamroth's sign
    • Combines qualities of nail-fold angle and phalangeal depth ratio
    • Have patient oppose index fingers so that they're nail-to-nail, pointing downwards
    • Negative/normal: diamond-shaped window (arrowhead) is created
    • Positive/abnormal: obliteration of diamond shape
Palpation
  • Grip sides of subject’s distal end of finger between thumb and middle finger with one hand and exert downward pressure at base of nail bed with index finger of other hand
  • Clubbing
    • Increased sponginess
    • Perception that nail is “floating” within soft tissue
    • Palpable proximal edge of nail

References

  1. Bickley LS. The thorax and lungs. In: Bickley LS, Szilagyi PG. Bates' Guide to Physical Examination and History Taking. 10th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:283-321.
  2. Lampe RM, Kagan A. Detection of clubbing—Schamroth’s sign. Closing the window and opening the angle. Clinical Pediatrics. 1983;22(2):125.
  3. Myers KA, Farquhar DRE. The rational clinical examination: Does this patient have clubbing? JAMA. 2001;286(3):341-347.