Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death

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Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: Selection and modification rules
	ICD-9	ICD-10
Selection rules	General Rule: Select the condition entered alone on the lowest used line of Part I unless it is highly improbable that this condition could have given rise to all the conditions entered above it.	General Principle: When more than one condition is entered on the certificate, the condition entered alone on the lowest used line of Part I should be selected only if it could have given rise to all the conditions entered above it.
Rule 1: If there is a reported sequence terminating in the condition first entered on the certificate, select the underlying cause of this sequence. If there is more than one such sequence, select the underlying cause of the first-mentioned sequence.	Rule 1: If the General Principle does not apply and there is a reported sequence terminating in the condition first entered on the certificate, select the originating cause of this sequence. If there is more than one sequence terminating in the condition mentioned first, select the originating cause of the first-mentioned sequence.
Rule 2: If there is no reported sequence terminating in the condition first entered on the certificate, select this first mentioned condition.	Rule 2: If there is no reported sequence terminating in the condition first entered on the certificate, select this first-mentioned condition.
Rule 3: If the condition selected by the General rule or Rules 1 or 2 can be considered a direct sequel of another reported condition, whether in Part I or Part II, select this primary condition. If there are two or more such primary conditions, select the first mentioned cause.	Rule 3: If the condition selected by the General Principle or by Rule 1 or Rule 2 is obviously a direct consequence of another reported condition, whether in Part I or Part II, select this primary condition.
Modification rules	Rule 4, Senility: Where the selected underlying cause is classifiable to 797 (Senility) and a condition classifiable elsewhere than to 780 to 799 is reported on the certificate, reselect the underlying cause as if the senility had not been reported, except to take account of the senility if it modifies the coding. Rule 5, Ill-defined conditions: Where the selected underlying cause is classifiable to 780 to 796, 798 to 799 (the ill-defined conditions) and a condition classifiable elsewhere than to 780 to 799 is reported on the certificate, reselect the underlying cause as if the ill-defined condition had not been reported, except to take account of the ill-defined condition if it modifies the coding.	Rule A, Senility and other ill-defined conditions: Where the selected cause is classifiable to Chapter XVIII (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified) except for R95 (Sudden infant death syndrome), and a condition classified elsewhere than to R00 to R94 or R96 to R99 is reported on the certificate, reselect the cause of death as if the condition classified to Chapter XVIII had not been reported, except to take account of that condition if it modifies the coding.
Rule 6, Trivial conditions: Where the selected underlying cause is a trivial condition unlikely to cause death, proceed as follows: (a) if the death was the result of an adverse reaction to treatment of the trivial condition, select the adverse reaction; (b) if the trivial condition is not reported as the cause of a more serious complication, and a more serious unrelated condition is reported on the certificate, reselect the underlying cause as if the trivial condition had not been reported.	Rule B, Trivial conditions: Where the selected cause is a trivial condition unlikely to cause death and a more serious condition is reported, reselect the underlying cause as if the trivial condition had not been reported. If the death was the result of an adverse reaction to treatment of the trivial condition, select the adverse reaction.
Rule 7, Linkage: Where the selected underlying cause is linked by a provision in the classification in the Notes for use in primary mortality coding on pages 713 to 721 with one or more of the other conditions on the certificate, code the combination. Where the linkage provision is only for the combination of one condition specified as due to another, code the combination only when the correct causal relationship is stated or can be inferred from application of the selection rules. Where a conflict in linkages occurs, link with the condition that would have been selected if the underlying cause initially selected had not been reported. Apply any further linkage that is applicable.	Rule C, Linkage: Where the selected cause is linked by a provision in the classification or in the notes for use in underlying cause mortality coding with one or more of the other conditions on the certificate, code the combination. Where the linkage provision is only for the combination of one condition specified as due to another, code the combination only when the correct causal relationship is stated or can be inferred from application of the selection rules. Where a conflict in linkages occurs, link with the condition that would have been selected if the cause initially selected had not been reported. Make any further linkage that is applicable.
Rule 8, Specificity: Where the selected underlying cause describes a condition in general terms and a term which provides more precise information about the site or nature of this condition is reported on the certificate, prefer the more informative term. This rule will often apply when the general term can be regarded as an adjective qualifying the more precise term.	Rule D, Specificity: Where the selected cause describes a condition in general terms and a term that provides more precise information about the site or nature of this condition is reported on the certificate, prefer the more informative term. This rule will often apply when the general term becomes an adjective, qualifying the more precise term.
Rule 9, Early and late stages of disease: Where the selected underlying cause is an early stage of a disease and a more advanced stage of the same disease is reported on the certificate, code to the more advanced stage. This rule does not apply to a "chronic" form reported as due to an "acute" form unless the Classification gives special instructions to that effect.	Rule E, Early and late stages of disease: Where the selected cause is an early stage of a disease and a more advanced stage of the same disease is reported on the certificate, code to the more advanced stage. This rule does not apply to a "chronic" form reported as due to an "acute" form unless the classification gives special instructions to that effect.
Rule 10, Late effects: Where the selected underlying cause is an early form of a condition for which the Classification provides a separate late effects category and there is evidence that death occurred from residual effects of this condition rather than in its active phase, code to the appropriate late effects category. The following late effects categories, including those in the Supplementary E code, have been provided: 137, 138, 139, 268.1, 326, 438, 905 to 909, E929, E959, E969, E977, E989, and E999.	Rule F, Sequelae: Where the selected cause is an early form of a condition for which the classification provides a separate "Sequelae of …" category, and there is evidence that death occurred from residual effects of this condition rather than from those of its active phase, code to the appropriate "Sequelae of …" category. "Sequelae of …" categories are as follows: B90 to B94, E64.-, E68, G09, I69, O97 and Y85 to Y89.
Rule 11, Old pneumonia, influenza and maternal conditions: Where the selected underlying cause is pneumonia or influenza (480 to 487) and there is evidence that the date of onset was 1 year or more prior to death or a resultant chronic condition is reported, reselect the underlying cause as if the pneumonia or influenza had not been reported. Where the selected underlying cause is a maternal cause (630 to 678) and there is evidence that death occurred more than 42 days after termination of pregnancy or a resultant chronic condition is reported, reselect the underlying cause as if the maternal cause had not been reported. Take into account the pneumonia, influenza or maternal condition if it modifies the coding.	No corresponding rule.
Rule 12, Errors and accidents in medical care: Where the selected underlying cause was subject to medical care and the reported sequence in Part I indicates explicitly that the death was the result of an error or accident occurring during medical care (conditions classifiable to categories E850 to E858, E870 to E876), regard the sequence of events leading to death as starting at the point at which the error or accident occurred. This does not apply to attempts at resuscitation.	No corresponding rule.

Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: Selection and modification rules

ICD-9

ICD-10

Selection rules

General Rule: Select the condition entered alone on the lowest used line of Part I unless it is highly improbable that this condition could have given rise to all the conditions entered above it.

General Principle: When more than one condition is entered on the certificate, the condition entered alone on the lowest used line of Part I should be selected only if it could have given rise to all the conditions entered above it.

Rule 1: If there is a reported sequence terminating in the condition first entered on the certificate, select the underlying cause of this sequence. If there is more than one such sequence, select the underlying cause of the first-mentioned sequence.

Rule 1: If the General Principle does not apply and there is a reported sequence terminating in the condition first entered on the certificate, select the originating cause of this sequence. If there is more than one sequence terminating in the condition mentioned first, select the originating cause of the first-mentioned sequence.

Rule 2: If there is no reported sequence terminating in the condition first entered on the certificate, select this first mentioned condition.

Rule 2: If there is no reported sequence terminating in the condition first entered on the certificate, select this first-mentioned condition.

Rule 3: If the condition selected by the General rule or Rules 1 or 2 can be considered a direct sequel of another reported condition, whether in Part I or Part II, select this primary condition. If there are two or more such primary conditions, select the first mentioned cause.

Rule 3: If the condition selected by the General Principle or by Rule 1 or Rule 2 is obviously a direct consequence of another reported condition, whether in Part I or Part II, select this primary condition.

Modification rules

Rule 4, Senility: Where the selected underlying cause is classifiable to 797 (Senility) and a condition classifiable elsewhere than to 780 to 799 is reported on the certificate, reselect the underlying cause as if the senility had not been reported, except to take account of the senility if it modifies the coding.

Rule 5, Ill-defined conditions: Where the selected underlying cause is classifiable to 780 to 796, 798 to 799 (the ill-defined conditions) and a condition classifiable elsewhere than to 780 to 799 is reported on the certificate, reselect the underlying cause as if the ill-defined condition had not been reported, except to take account of the ill-defined condition if it modifies the coding.

Rule A, Senility and other ill-defined conditions: Where the selected cause is classifiable to Chapter XVIII (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified) except for R95 (Sudden infant death syndrome), and a condition classified elsewhere than to R00 to R94 or R96 to R99 is reported on the certificate, reselect the cause of death as if the condition classified to Chapter XVIII had not been reported, except to take account of that condition if it modifies the coding.

Rule 6, Trivial conditions: Where the selected underlying cause is a trivial condition unlikely to cause death, proceed as follows: (a) if the death was the result of an adverse reaction to treatment of the trivial condition, select the adverse reaction; (b) if the trivial condition is not reported as the cause of a more serious complication, and a more serious unrelated condition is reported on the certificate, reselect the underlying cause as if the trivial condition had not been reported.

Rule B, Trivial conditions: Where the selected cause is a trivial condition unlikely to cause death and a more serious condition is reported, reselect the underlying cause as if the trivial condition had not been reported. If the death was the result of an adverse reaction to treatment of the trivial condition, select the adverse reaction.

Rule 7, Linkage: Where the selected underlying cause is linked by a provision in the classification in the Notes for use in primary mortality coding on pages 713 to 721 with one or more of the other conditions on the certificate, code the combination.

Where the linkage provision is only for the combination of one condition specified as due to another, code the combination only when the correct causal relationship is stated or can be inferred from application of the selection rules.

Where a conflict in linkages occurs, link with the condition that would have been selected if the underlying cause initially selected had not been reported. Apply any further linkage that is applicable.

Rule C, Linkage: Where the selected cause is linked by a provision in the classification or in the notes for use in underlying cause mortality coding with one or more of the other conditions on the certificate, code the combination.

Where a conflict in linkages occurs, link with the condition that would have been selected if the cause initially selected had not been reported. Make any further linkage that is applicable.

Rule 8, Specificity: Where the selected underlying cause describes a condition in general terms and a term which provides more precise information about the site or nature of this condition is reported on the certificate, prefer the more informative term. This rule will often apply when the general term can be regarded as an adjective qualifying the more precise term.

Rule D, Specificity: Where the selected cause describes a condition in general terms and a term that provides more precise information about the site or nature of this condition is reported on the certificate, prefer the more informative term. This rule will often apply when the general term becomes an adjective, qualifying the more precise term.

Rule 9, Early and late stages of disease: Where the selected underlying cause is an early stage of a disease and a more advanced stage of the same disease is reported on the certificate, code to the more advanced stage. This rule does not apply to a "chronic" form reported as due to an "acute" form unless the Classification gives special instructions to that effect.

Rule E, Early and late stages of disease: Where the selected cause is an early stage of a disease and a more advanced stage of the same disease is reported on the certificate, code to the more advanced stage. This rule does not apply to a "chronic" form reported as due to an "acute" form unless the classification gives special instructions to that effect.

Rule 10, Late effects: Where the selected underlying cause is an early form of a condition for which the Classification provides a separate late effects category and there is evidence that death occurred from residual effects of this condition rather than in its active phase, code to the appropriate late effects category.

The following late effects categories, including those in the Supplementary E code, have been provided: 137, 138, 139, 268.1, 326, 438, 905 to 909, E929, E959, E969, E977, E989, and E999.

Rule F, Sequelae: Where the selected cause is an early form of a condition for which the classification provides a separate "Sequelae of …" category, and there is evidence that death occurred from residual effects of this condition rather than from those of its active phase, code to the appropriate "Sequelae of …" category.

"Sequelae of …" categories are as follows: B90 to B94, E64.-, E68, G09, I69, O97 and Y85 to Y89.

Rule 11, Old pneumonia, influenza and maternal conditions: Where the selected underlying cause is pneumonia or influenza (480 to 487) and there is evidence that the date of onset was 1 year or more prior to death or a resultant chronic condition is reported, reselect the underlying cause as if the pneumonia or influenza had not been reported. Where the selected underlying cause is a maternal cause (630 to 678) and there is evidence that death occurred more than 42 days after termination of pregnancy or a resultant chronic condition is reported, reselect the underlying cause as if the maternal cause had not been reported. Take into account the pneumonia, influenza or maternal condition if it modifies the coding.

No corresponding rule.

Rule 12, Errors and accidents in medical care: Where the selected underlying cause was subject to medical care and the reported sequence in Part I indicates explicitly that the death was the result of an error or accident occurring during medical care (conditions classifiable to categories E850 to E858, E870 to E876), regard the sequence of events leading to death as starting at the point at which the error or accident occurred. This does not apply to attempts at resuscitation.

No corresponding rule.

Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: ICD-10 rule revisions - Selection rule 3
As originally published by WHO in 1993	As revised, effective 2003
Assumed direct consequences of another condition: Pneumonia and bronchopneumonia may be accepted as complications of any disease. In particular, bronchopneumonia should be assumed to be an obvious consequence of wasting diseases (such as malignant neoplasm and malnutrition) and diseases causing paralysis (such as brain or spinal cord injuries, cerebral haemorrhage or thrombosis, and poliomyelitis), as well as communicable diseases and non-trivial injuries.	Assumed direct consequences of another condition: Any pneumonia in J12 to J18 should be considered an obvious consequence of conditions that impair the immune system. Pneumonia in J18.0 and J18.2 to J18.9 should be considered an obvious consequence of wasting diseases (such as malignant neoplasm and malnutrition) and diseases causing paralysis (such as cerebral haemorrhage or thrombosis), as well as serious respiratory conditions, communicable diseases, and serious injuries. Pneumonia in J18.0 and J18.2 to J18.9, J69.0, and J69.8 should also be considered an obvious consequence of conditions that affect the process of swallowing.

Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: ICD-10 rule revisions - Selection rule 3

As originally published by WHO in 1993

As revised, effective 2003

Assumed direct consequences of another condition: Pneumonia and bronchopneumonia may be accepted as complications of any disease. In particular, bronchopneumonia should be assumed to be an obvious consequence of wasting diseases (such as malignant neoplasm and malnutrition) and diseases causing paralysis (such as brain or spinal cord injuries, cerebral haemorrhage or thrombosis, and poliomyelitis), as well as communicable diseases and non-trivial injuries.

Assumed direct consequences of another condition: Any pneumonia in J12 to J18 should be considered an obvious consequence of conditions that impair the immune system. Pneumonia in J18.0 and J18.2 to J18.9 should be considered an obvious consequence of wasting diseases (such as malignant neoplasm and malnutrition) and diseases causing paralysis (such as cerebral haemorrhage or thrombosis), as well as serious respiratory conditions, communicable diseases, and serious injuries. Pneumonia in J18.0 and J18.2 to J18.9, J69.0, and J69.8 should also be considered an obvious consequence of conditions that affect the process of swallowing.

Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: ICD-10 rule revisions - Modification rule A
As originally published by WHO in 1993	As revised, effective 2001
Where the selected cause is classifiable to Chapter XVIII (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified) except for R95 (Sudden infant death syndrome), and a condition classified elsewhere than to R00 to R94 or R96 to R99 is reported on the certificate, reselect the cause of death as if the condition classified to Chapter XVIII had not been reported, except to take account of that condition if it modifies the coding.	Where the selected cause is ill-defined and a condition classified elsewhere is reported on the certificate, reselect the cause of death as if the ill-defined condition had not been reported, except to take account of that condition if it modifies the coding. The following conditions are regarded as ill-defined: I46.9 (Cardiac arrest, unspecified); I95.9 (Hypotension, unspecified); I99 (Other and unspecified disorders of circulatory system); J96.0 (Acute respiratory failure); J96.9 (Respiratory failure, unspecified); P28.5 (Respiratory failure of newborn); R00 to R94 or R96 to R99 (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified). Note that R95 (Sudden infant death syndrome) is not regarded as ill-defined.

Table 3. Comparison of ICD-9 and ICD-10 rules for selection of underlying cause of death: ICD-10 rule revisions - Modification rule A

As originally published by WHO in 1993

As revised, effective 2001

Where the selected cause is classifiable to Chapter XVIII (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified) except for R95 (Sudden infant death syndrome), and a condition classified elsewhere than to R00 to R94 or R96 to R99 is reported on the certificate, reselect the cause of death as if the condition classified to Chapter XVIII had not been reported, except to take account of that condition if it modifies the coding.

Where the selected cause is ill-defined and a condition classified elsewhere is reported on the certificate, reselect the cause of death as if the ill-defined condition had not been reported, except to take account of that condition if it modifies the coding. The following conditions are regarded as ill-defined: I46.9 (Cardiac arrest, unspecified); I95.9 (Hypotension, unspecified); I99 (Other and unspecified disorders of circulatory system); J96.0 (Acute respiratory failure); J96.9 (Respiratory failure, unspecified); P28.5 (Respiratory failure of newborn); R00 to R94 or R96 to R99 (Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified). Note that R95 (Sudden infant death syndrome) is not regarded as ill-defined.