Katz hand diagram

Abstract

The Katz hand diagram is a rapid and non-invasive screening tool utilized primarily for the diagnosis of Carpal Tunnel Syndrome (CTS). The procedure involves presenting the patient with a diagram illustrating both hands and arms. The patient is then instructed to accurately mark the specific locations of their symptoms, differentiating between various types of discomfort, including stiffness, pain, tingling, and sensory disturbances or numbness. The resulting drawing is subsequently classified by the clinician into one of three standardized diagnostic categories: Pattern A (Classic), Pattern B (Probable), and Pattern C (Unlikely), allowing for a quick clinical assessment of median nerve involvement.

Keywords

Katz hand diagram, Carpal Tunnel Syndrome, CTS diagnosis, sensory mapping, peripheral neuropathy, median nerve, upper extremity, clinical screening.

Authors

Katz JN, Stirrat CR (1990)

Purpose

The primary purpose of the Katz hand diagram is to serve as an efficient, low-cost screening instrument for identifying patients likely suffering from Carpal Tunnel Syndrome (CTS). It provides a visual and quantifiable method for documenting the distribution of subjective sensory complaints, which is crucial for distinguishing CTS from other causes of hand and wrist pain or paresthesia.

This diagram is frequently used in primary care settings and specialized clinics before more expensive or invasive diagnostic procedures, such as electrodiagnostic studies (nerve conduction tests), are considered. Its simplicity allows for rapid administration and immediate clinical interpretation regarding the likelihood of median nerve entrapment at the wrist.

Construct

The central construct measured by the Katz hand diagram is the typical distribution pattern of sensory symptoms resulting from median nerve compression within the carpal tunnel. The classification system relies on the anatomical principle that CTS symptoms usually affect the median nerve territory distal to the wrist, often sparing the palmar cutaneous branch.

The instrument categorizes the patient’s symptomatic distribution based on how closely it aligns with known anatomical patterns of median nerve involvement. Pattern A (Classic) indicates a high probability of CTS by showing symptoms localized to the median nerve distribution, while Pattern C (Unlikely) suggests an alternative diagnosis, such as cervical radiculopathy or ulnar nerve pathology, as the source of the patient’s discomfort.

Validity

The clinical validity of the Katz hand diagram is generally high, particularly when used as a screening tool. Studies have consistently demonstrated strong correlation between a “Classic” (Pattern A) or “Probable” (Pattern B) drawing and positive findings on definitive electrodiagnostic testing for Carpal Tunnel Syndrome.

Specifically, the diagram exhibits high sensitivity (often exceeding 80%) in identifying true positive cases of CTS. While its specificity can vary depending on the patient population, it remains a valuable tool for differentiating CTS from non-specific hand pain or other forms of peripheral nervous system disorders affecting the upper extremity. The high predictive value of the Classic pattern confirms its utility in clinical screening.

Reliability

The reliability of the Katz hand diagram is primarily assessed through inter-rater reliability, focusing on the consistency with which different clinicians classify the patient-drawn patterns. Early research indicated good to excellent inter-rater agreement (Kappa values often above 0.70) when clinicians apply the standardized classification rules defined by Katz and Stirrat.

Furthermore, test-retest reliability is considered acceptable, provided the patient’s symptoms remain stable between administrations. The primary source of variability is usually the patient’s ability to accurately map their symptoms, rather than the clinician’s interpretation of the resulting pattern. The defined classification criteria minimize subjective interpretation, contributing to its robust clinical reliability.

Factor Analysis

Traditional psychometric factor analysis is not typically applied to the Katz hand diagram, as it is a clinical classification tool rather than a multi-item psychometric scale designed to measure latent variables. Instead of factor loading, its structure is based on established anatomical and physiological patterns of nerve distribution.

The “factor structure” is inherent in the three outcome categories (A, B, C), which represent distinct clinical manifestations correlating with the likelihood of median nerve entrapment. This categorical structure serves as the basis for its diagnostic utility, effectively grouping symptom distributions based on their pathological relevance to Carpal Tunnel Syndrome.

Instrument

Test Type: Observation instrument (Patient-reported symptom mapping interpreted by a clinician)

Format: Paper-based diagram requiring patient drawing and subsequent clinical classification.

Language Available: Standard diagrams are language-neutral, though patient instructions must be provided in the appropriate language (e.g., Dutch/Nederlands version referenced in source data).

Population Group: Clinical populations presenting with symptoms related to the upper extremity and potential nerve entrapment.

Age Group: Adults, Elderly (Volwassenen, Ouderen)

Population Details: Suitable for individuals experiencing sensory functions impairment, pain, or paresthesia in the hands, wrists, or arms, specifically those suspected of having disorders of the peripheral nervous system.

Test Methodology: The patient marks the location of stiffness, pain, tingling, and numbness on the provided hand diagram. The resulting pattern is classified by the examiner (Katz Pattern A, B, or C).

Keywords

Peripheral neuropathy, median nerve entrapment, hand pain, numbness, diagnostic screening, clinical assessment, upper extremity disorders, sensory functions.

Authors

Author ORCID Identifier: Not provided in source content.

Affiliation Email addresses: Not provided in source content.

Correspondence Address: Not provided in source content.

Permissions & Fee and Test Year

The Katz hand diagram was introduced in 1990 by Katz and Stirrat. As a simple, non-proprietary diagnostic tool frequently reproduced in medical literature, the diagram itself is generally free for clinical use, though formal permission may be required for large-scale commercial reproduction or modification.

The original PDF of the Explanation Form can be downloaded here: Toelichtingsformulier (PDF).

The original PDF of the Measurement Instrument can be downloaded here: Meetinstrument (PDF).

Reference’s

• Katz JN, Stirrat CR. A self-administered hand diagram for the diagnosis of carpal tunnel syndrome. The Journal of Hand Surgery. 1990;15(2):360-363.
• The instrument is associated with diagnosing conditions related to the Peripheral nervous system and Zenuwstelsel en zintuigen (Nervous system and senses).

Items of the Katz hand diagram

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

Uitvoering: de patiënt krijgt een diagram voorgelegd van beide handen en armen. Vervolgens dient de patiënt in het diagram te tekenen waar de klachten gelokaliseerd zijn. Hierbij wordt onderscheid gemaakt tussen stijfheid, pijn, tintelingen en gevoelsstoornissen/doofheid. Het ingetekende diagram wordt geclassificeerd in 3 categorieën/patronen: A = klassiek patroon, B = waarschijnlijk patroon, C = onwaarschijnlijk patroon.