Anti-C1q antibodies are common in patients with lupus (30 to 50%) and are found in 50 to 100% of patients with lupus glomerulonephritis, the most serious complication of lupus.
This renal specificity makes the anti-C1q antibody a more specific marker than the anti-double-standed-DNA (ds DNA) antibody level for the monitoring of lupus renal complications. Recent studies have in fact shown that the elevation of anti-C1q antibodies occurs earlier than that of anti-ds DNA antibodies during renal damage relapse, and there is an obvious relationship between the level of antibodies and the extent of the damage.
Conversely, the anti-C1q antibodies present a good negative predictive value: patients without anti-C1q antibodies do not develop renal complications.

Thus, besides the level of anti-ds DNA and complement C3 and C4 fractions, for monitoring the progression of lupus, the determination of anti-C1q antibodies is useful for the diagnosis of renal damage and for monitoring the therapeutic response.
In addition to lupus, it is noteworthy that anti-C1q antibodies can be found in other autoimmune diseases (hypocomplementemic urticarial vasculitis/MacDuffie syndrome, Felty’s syndrome, Sjögren’s syndrome, rheumatoid arthritis), renal diseases (membranoproliferative glomerulonephritis) and sometimes in elderly subjects.

NMP22 is a tumour marker for bladder cancer. This cancer ranks 4th in men following lung, prostate and colon cancer. It only ranks 8th in women. According to the teams, the sex ratio is 1:3. The mean age at diagnosis is 68 years and the incidence increases directly with age.
Smoking is the main risk factor. It is present in 50% of cases. Equally affected are those with work exposure to aromatic amino acids which are used in the chemical industry, leather industry, printing, hairdressing professions and metal works. They are also present when driving a car with exposure to diesel fumes. The tumour can appear 15 to 40 years after the initial exposure.
Haematuria is present in 85% of patients with the tumour. It is usually terminal, painless and intermittent.
The French Urological Association (Association Française d’Urologie, 2002) formulated the following recommendations:

“Out-patient presenting with:
- macroscopic haematuria or
- microscopic haematuria associated with urinary disorders or
- asymptomatic permanent microscopic haematuria in the population at risk
(profession with exposure, smoking, over age 50)
should undergo a medical examination and consultation with a urologist for the investigation of a bladder tumour.”

According to the American Cancer Society’s (ACS) recommendations of 2006, urine cytology confirmed by cystoscopy remains the test for the identification and diagnosis of bladder tumours. In any case, the poor sensitivity of cytology has led to the development of urinary tumour markers. NMP22 has been shown to be useful in the detection of recurrent low-grade tumours. The cytology consists of examining the cancerous cells which are shed from the bladder epithelium using samples collected during urination (other than the first morning urination) or bladder lavage. Bladder cells take around one year to renew and a urine sample therefore contains very few cells. Additionally, these same cells will come into contact with an environment with high acidity and low osmolarity, which does not provide the best conditions for their preservation for microscopic examination. Consequently, these analytical conditions mean that this test has poor sensitivity for low-grade tumours (27%), although sensitivity is 77% for high-grade tumours. Its specificity, however, is 93%. There are also up to 12% false-positives in cases of bladder inflammation and urolithiasis.
Until now, the only tumour marker available for bladder cancer was the bladder tumour antigen (BTA). A structural analogue of the human complement factor H-related protein (hCFH-rp), this protein reduces the activity of the alternative complement pathway.
The major inconvenience of this test is that it gives false-positives with haematuria, which is the main warning sign of this cancer. Very high concentrations may also be seen with benign urinary diseases: acute or chronic cystitis, lithiasis, acute pyelonephritis, acute epididymo-orchitis, benign prostatic hypertrophy with urethral catheter.
NMP22, or nuclear matrix protein, forms the internal framework of the nucleus. It aids in the spatial organisation of intranuclear functions, such as DNA replication, RNA synthesis and the regulation of gene expression. The NMP22 protein is present in low concentrations in the urine of healthy individuals and increases in patients with urinary tract carcinoma. NMP22 is assayed using the ELISA technique. According to studies, this test has a sensitivity of 47 to 100% and a specificity between 60 and 70%. NMP22 has been approved by the FDA when used with cystoscopy. This test is mainly recommended for the follow-up of bladder cancer treatment, as well as in the detection of recurrence.

Reference values: 10 – 540 µg/l.