Seropositive & seronegative:

What do they mean?

Professor Gabriel Panayi (formerly NRAS Chief Medical Advisor, now NRAS Patron), Emeritus Professor of Rheumatology, Guy’s, King’s, St Thomas’ School of Medicine and consultant rheumatologist Guy’s Hospital, London
Original article: 13/12/2011
Reviewed: N/A
Next review due: 13/12/2014

Introduction

The diagnosis of any disease usually progresses along a well defined path that has three parts: a history of the complaint, blood tests and, usually, imaging (x-rays or scans). "Seropositive/seronegative" is a term that refers to the results of a blood test.

What is seropositive/seronegative?

The blood test that is ordered by the doctor in order to help establish the diagnosis of rheumatoid arthritis (RA) is looking for the presence of two proteins in the blood. One of them is called rheumatoid factor (RF). This is a very old but tried and tested investigation that was first introduced into rheumatology in the 1940s. The other test is called anti-CCP and is more recent. Although all hospitals perform RF tests not all carry out anti-CCP tests.

What do the test results mean?

The presence of either of these tests may indicate that RA is present. However seropositivity is only one criterion of several that makes the diagnosis of RA likely (some of the other criteria are outlined in the next section). If the other criteria for the diagnosis are present then seropositivity is an additional clinching factor. A positive anti-CCP test is marginally stronger than positive RF test for the diagnosis.

Does a positive rheumatoid factor or anti-CCP mean you must have RA?

A positive RF or anti-CCP test does not mean that you have RA. Other features must be present such as symptoms of pain and swelling in the joints, involvement of many joints with inflammation, morning stiffness in the joints for longer than 45 min, x-ray evidence of the characteristic bone damage in the joints and extra-articular features of RA (meaning features that are outside the joints), such as nodules. Other blood tests commonly used prior to diagnosis include ESR and CRP, which look for signs of inflammation in the joints. For more information on blood tests please see our article: ‘Laboratory tests used in the diagnosis and monitoring of rheumatoid arthritis.’

Does this test tell me how severe my arthritis is likely to be?

As a rule patients who are seropositive for RF and/or anti-CCP are more likely to have more severe RA but this test cannot accurately predict the future course of the disease in an individual patient.

What differences are there between people that are seropositive and seronegative?

As well as seropositive patients having a greater likelihood of developing more serious disease, they are also more likely to have extra-articular complications than those who are seronegative.

Does this affect the medications that will work for me?

Whilst the efficacy of most medications is not affected by whether someone is seropositive or seronegative, evidence suggests that patients who are seronegative for both RF and anti-CCP do not respond as well to rituximab as patients who are sero-positive for one or both. However, since some seronegative patients may respond to rituximab this treatment should not be withheld from them. Rituximab is one of the newer, biologic drugs sometimes used at a later stage in treating RA.

References available on request

If this information has helped you, please help us by making a donation. Thank you.