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.


  • 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

  • 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 arrowhead
  • Grip sides of subject’s distal end of finger between thumb and middle finger with one hand and exert downward pressure at base of nailbed with index finger of other hand
  • Clubbing
    • Increased sponginess
    • Perception that nail is “floating” within soft tissue
    • Palpable proximal edge of nail


  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.