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Palpation is examination by touch with the hands or fingers. It uses physical contact to assess features such as an organ's apparent size, position, consistency and tenderness. The observed feature and the resulting clinical diagnosis are separate: feeling a moving or resistant region does not by itself identify the complete underlying anatomy or disease.^[ref]

The force applied during palpation is part of the measurement. In an original simplified indentation example, suppose a probe produces $2\mathrm{mm}$ of displacement under a $1\mathrm{N}$ load. The secant stiffness for that observation isA second specimen requiring $2\mathrm{N}$ at the same displacement has twice this apparent stiffness. That ratio is not automatically a ratio of intrinsic elastic modulus values: contact geometry, specimen thickness, support and deformation rate can alter the force-displacement curve. Touch supplies a mechanical observation whose interpretation requires an appropriate model.

A clinical measurement study makes the distinction concrete. S. D. Eilen and colleagues compared precordial palpation with two-dimensional echocardiography in 41 patients. They compared the location and palpable diameter of the apical impulse with left ventricle end-diastolic volume. A lateral impulse location was sensitive but not specific for enlargement. Within the reported subgroup without ventricular hypertrophy, an impulse diameter above $3\mathrm{cm}$ in the left-lateral position had reported diagnostic sensitivity $92\%$ and diagnostic specificity $91\%$. Those are results for that study's condition and subgroup, rather than universal performance figures for touch.^[ref]

A small probability example explains why both attributes matter. In a stipulated set with 20 enlarged and 80 non-enlarged hearts, a rule detecting 18 enlarged hearts but also flagging 24 non-enlarged hearts has diagnostic sensitivity $18/20=90\%$ and diagnostic specificity $56/80=70\%$. Only $18/42\simeq 43\%$ of its positive results identify enlargement. These invented counts are not a reconstruction of the 41-patient study. They show why a palpable feature must be tested against an independent reference and interpreted with the population being examined.

Repeating a specified observation can assess reproducibility, while comparison with echocardiography assesses a different question: correspondence with the chosen anatomical reference. Holding body position and observation method consistent helps distinguish those sources of variation. A reliable description of what was felt is necessary evidence, but reproducibility alone does not establish the causal explanation.